The earliest group comprises genera with jaws set with teeth, and with long tails sometimes provided with a rudderlike expansion at the end.
During all geological time since life began on earth old species have constantly become extinct and with them the genera and families to which they belong, and other species, genera, and families have replaced them.
Even in these widely separated regions the genera and species of coal plants are close akin and often identical.
The few genera now surviving are the descendants of the tribes which swarmed in the Devonian seas.
Among them were a number of genera of clumsy, ponderous brutes, some almost elephantine in their bulk.
Types already present branched widely into new genera and species, and new and higher types appeared.
The antique forms of the earlier Carboniferous amphibians continue, but with many new genera and a marked increase in size.
The structures of man's body show that he is not descended from any of the existing genera of apes.
The plants of the Tertiary belonged, for the most part, to genera now living; but their distribution was very different from that of the flora of to-day.
In the birds, the Ethiopian type is shown by the prevalence of larks and stone chats, and by the complete absence of the many peculiar genera of the Indian region.
The Bovidae or hollow-horned ruminants, are represented by several genera of antelopes, and by species of true Bos--such as B.
The Mullidae or red mullets are largely represented by genera differing from those of Europe.
Mackerels of various genera abound, as well as gobies, blenniesm and mullets.
The connexion with Africa is marked by the occurrence of many genera common to Africa and India, and confined to those two regions, and similarities of form are not uncommon there in cases in which the genera are not peculiar.
In the order of Rodents squirrels are very numerous and porcupines of two genera are met with.
Other allied genera are abundant and extend from the Indian seas to eastern Africa.
The genera common to the Himalaya and Europe are much more abundant, and extend throughout the chain, and to all elevations.
On the other islands similar characteristics are to be observed, Australian genera extending to the Philippines, and even to southern China.
The number of families relative to the area is very small, and the number of genera and species equally restricted, in very many cases a single species being the only representative of an order.
In all cases the upper molar is larger than the sectorial, and in the more typical genera is much longer than broad.
Possibly these genera may be nearly related to Cyon.
To deal with fossil representatives of living genera, or extinct genera nearly related to groups still existing, would here be impracticable.
Remains of several of the existinggenera have been found in Oligocene and later beds of Europe, Sumatra and North America.
The other genera of this section have the same dental formula, but are distinguished by the characters, of the cheek-teeth and the feet.
The creodontgenera Stypolophus and Proviverra show some of these modern characters; but it is not till we reach the European Oligocene genus Amphictis, with the dental formula i.
Suborbital foramen small, and the palate, as in all the succeeding genera of this group, produced backwards about midway between the last molar and the glenoid fossa.
Some of the butterflies of the United States belong to genera which are not confined to this country, but which occur also in the Eastern Hemisphere.
For a limited description of several genera and species, see last month.
This extensive genus is curious, grotesque, interesting, and varied in character and habit; is now divided into six distinct genera according to their natural appearance and habit.
They have syngenesious purple flowers in long close spikes, differing from other spiked flowering genera by blooming first at the extremity.
Those genera of plants which we have enumerated under the head of repotting in this or next month, are composed of the finest Hot-house plants that have come under our observation.
Colchicum, with species of several other genera not introduced into the country.
Melastoma, was once an extensive genus, on which the natural order Melastomaceae is founded; but is now much divided into other genera contained in the natural tribe Micomeae.
These three genera in most collections are not well known specifically, but it is easy to discriminate which genus they are connected with.
Of most genera they are not known, though in a few they have been found in connection with recognizable parts of their tissue.
This Palaeozoic flora has in general characters similar to those of the European Permo-Carboniferous, but it has special features of its own, in particular the genus Glossopteris and also the genera Phyllotheca and Schizoneura.
Many of the Carboniferous genera are found to extend through the Permian and then die out, while at the same time others became quite extinct as the physical conditions changed.
VIII), and were of the families and even genera which are now living, of which not a few belong to the warm regions of the earth, and are subtropical.
To-day most individual species and many genera are limited to islands or parts of continents, but before the Glacial epoch many were distributed over both America and Europe.
In most of the genera numerous petioles are given off from the main axis, and these are often of a large size compared with it, and may sometimes be thicker than the axis itself.
The group of Gymnosperms includes a number of genera of different types, most of which may be arranged under seven principal families.
In the later divisions of the Pre-Carboniferous some of the plants seem to belong to the same genera as those of the Carboniferous period.
These two genera represent the climax of development of the Lycopod family.
Of these a number seem to belong to genera which are still living, and many of them are extremely like living species.
Among the palaeozoic members of the group are other genera closely allied to, but differing from Calamites in some particulars.
The freshening of the Caspian Sea, which was an outlying part of the Mediterranean quite late in the geological record, seems to have evolved several newgenera of Molluscs.
Long before the end of the Cretaceous most of the modern genera of Angiosperm trees have developed.
Yet these rich and numerous finds throw little light on the evolution of the insect, except in the general sense that they show species and even genera quite different from those of to-day.
In somegenera the teeth degenerate in the course of time, but this merely indicates a change of diet.
But all the other orders of insects are represented, and many of our modern genera are fully evolved.
There were at least twenty genera of them living in what is now the island of Britain, and was then part of the British-Scandinavian continent.
It may be added that every one of the above-named genera from Quiriquina, which have an apparently tertiary character, are found in the Pondicherry strata.
Imperfect fragments of the genera Byssoarca, Artemis, and Fusus.
Fifteen of the genera have on this coast living representatives in about the same latitudes with the fossil species; but twelve genera now range very differently to what they formerly did.
As the number of the fossil species and genera from the western and eastern coasts is considerable, it will be interesting to consider the probable nature of the climate under which they lived.
Several of the most tropical genera have no representative fossils at Navidad; and there are only single species of Cassis, Pyrula, and Sigaretus, two of Pleurotoma and two of Terebra, but none of these species are of conspicuous size.
Forbes had investigated such important genera as Philepitta and Xenicus, P.
In the north it is influenced, of course, by its proximity to Papuasia, whence there is a considerable admixture of genera which do not proceed beyond the tropics, and of these Casuarius is a striking example.
To compare the Palaearctic genera with those of the Australian and Neotropical regions would be simply a waste of time, for the points of resemblance are extremely few, and such as they are they lead to nothing.
The Indian or Cisgangetic province is the least rich of the three so far as peculiar genera are concerned.
At the lowest computation 37 genera seem to be peculiar to it, though it is certain that species of several are regularly wont to wander beyond its limits in winter seeking a southern climate.
This applies especially ~~ to those instances in which the members of families, genera and species are mentioned.
We note the absence of Ratitae, Tinami, Cracidae, Rhamphastidae, and any of those gruiform genera which are so characteristic of the continent.
Of the Meliphagidae the genera Prosthemadera, Pogonornis and Anthornis are peculiar.
The same characteristic may be observed in several other groups--especially those known as belonging to the genera Calandrella, Ammomanes and Certhilauda, some species of which are of a light sandy or cream colour.
Allied to the lapwing are several forms that have been placed by ornithologists in the genera Hoplopterus, Chettusia, Lobivanellus, Defilippia.
The teeth of the two genera were essentially different.
It seems at least difficult to conceive of a sea inhabited by many genera of fishes, each divided into several species, and yet furnished with but one species of shell.
I saw among them several good specimens of the genus Pterichthys, and of what is elsewhere one of the rarergenera of the Dipterians,--the Diplopterus.
Senior Assistant of the Zoological Department, British Museum; and author of the "List of the Genera of Birds," etc.
In the Philippines the group is represented by Podogymnura truei, distinguished from the other genera by the great elongation of the hind-foot, the tail being likewise long.
Finally the genera Pinguicula, Utricularia, Genlisea and Polypompholix belong to the gamopetalous order Lentibulariaceae.
The Sarraceniaceae contain the genera Sarracenia, Darlingtonia, Heliamphora, while the true pitcher plants or Nepenthaceae consist of the single large genus Nepenthes.
In Tupaia, Centetes, Hemicentetes, Ericulus and Solenodon the tibia and fibula are distinct, but in most other genera united.
Buetschli has made the very important discovery that in perfectly ripe eggs of Nephelis, Lymnaeus and Cucullanus and allied genera a spindle, similar to that of ordinary nuclei in the act of division, appears close to the surface of the egg.
They have been found in many other genera of Araneina (Claparede, Barrois).
Schultz[380] has more recently investigated a considerable variety of genera and finds three conditions of the egg membranes.
From what I have been able to see of Squatina and Acanthias, I am inclined to think that the embryos of either of these genera would form far more suitable objects for this research than Scyllium.
The last part of the description beginning at "The connection of" does not hold good for any of the genera which I have had an opportunity of investigating, as will appear from the sequel.
Loss of some enamel is more common on P4 than on M1-2, and has occurred in all genera (see Figs.
Key to the Genera of the Tribe Geomyini A Cheek teeth rooted; p4 with uninterrupted enamel loop; enamel plates on both anterior and posterior walls of m1 and m2; masseteric ridge weakly developed, low, not massive.
He placed his new family phylogenetically between the family Sciuridae and the family Spalacoides (a group in which Brandt included the genera Spalax, Sipheus, and Ellobius).
It is interesting to note that the genus Thomomys occurred in this region at approximately the same time; both genera occur in Saber-tooth Cave deposits.
However, Merriam's genera have been recognized in all subsequent classifications except for the current review (see Table 1).
Saccomyina, in which he included the genera Heteromys, Saccomys, Perognathus, and Dipodomys.
All three of the inferior molars are elliptical, and only the posterior enamel plate is present (as in all other genera of the tribe except Pliogeomys).
Examination of these modern species would not radically change the estimation of the degree of phyletic development of the genera and subgenera involved.
The Conard fissure, a Pleistocene bone deposit in northern Arkansas with description of twogenera & 20 new species of mammals.
However, neither genera nor subgenera of the tribe Geomyini can be distinguished on the basis of their inferior dentitions.
Merriam described much new material, especially from Mexico and Central America, and proposed seven new genera (see Table 1).
Loss of enamel is a trend common to all livinggenera of the tribe Geomyini, but the greatest loss has occurred in Cratogeomys.
Many of the old gigantic pachyderms have disappeared; and in their stead some familiar modern genera were introduced.
I have myself found specimens referred by Mr. Scudder, a most competent entomologist, to two genera and five species, in a few decayed fossil stumps in Nova Scotia, and several others have been discovered in other parts of the world.
Zoologically they are not varieties of the same species with man they are not species of the same genus, nor do they belong to genera of the same family, or even to families of the same order.
Such were the pretty, graceful fishes of the genera Palaeoniscus and Amblypterus.
It is curious that these composite creatures belong to a later period of the Mesozoic then the typical Ichthyosaurs and Plesiosaurs, as if the characters at one time separated in these genera had united in their successors.
There are many genera of which the leaves are variable, and consequently would be likely to lead us astray if we trusted in them alone.
In America a large number of the genera of the modern trees are present, and even some of those now peculiar to America, as the tulip-trees and sweet-gums.
Four of these fivegenera are montane in distribution.
Variation in the muscles and nerves of the leg in two genera of grouse (Tympanuchus and Pedioecetes).
The endemic species in Borneo are members of four, possibly five, genera that are also endemic.
There are about a dozen genera and a thousand species, mostly tropical plants with pungent and aromatic qualities.
Of or pertaining to Phyllorhina and other related generaof bats that have a leaflike membrane around the nostrils.
Commencement of analytical consciousness of the mental operations—genera and species.
Dismissing these subjects for the present, it will perhaps be most convenient to treat of the two groups which are represented by the genera Pyrrhocorax or choughs, and Corvus or true crows in the most limited sense.
In both these genera the possibility of reproduction is not restricted to a single female in the nest, but is shared by a number of females.
I have always found full-sized shells present in at least two-thirds of the individuals of these genera characterized by much-coiled shells—a proportion which I have never seen among our larger Helicidae.
In addition to these there are a few genera and species upon which I have insufficient notes, and these I shall reserve until opportunity comes to study them further.
Lateral views of the left ear ossicles (articulated) of the Recent genera of the subfamily Zapodinae.
The difference in stage of wear of the teeth in Macrognathomys and Pliozapus is a handicap in comparing the two genera but they are distinct.
Possibly these two genera diverged at an early date; nevertheless, they are closely related primitive forms.
In addition, attention is given to the probable center of origin of the subfamily Zapodinae and to the relationships and taxonomic positions of the genera Zapus, Napaeozapus, and Eozapus.
Status of the genera Eozapus, Zapus, and Napaeozapus The genus Zapus is one of three livinggenera in the subfamily Zapodinae.
Occlusal views of upper and lower right cheek-teeth, of the three Recent genera of the subfamily Zapodinae.
Dorsal and lateral views of the bacula of the Recent genera (and species of the genus Zapus) of the subfamily Zapodinae.
According to the complexity in dental pattern and in number and size of the cheek-teeth, these genera can be arranged in a structurally progressive series with Eozapus showing the least complexity and Napaeozapus the most (see figs.
Three views of the skull and a lateral view of the left lower jaw of each of the Recent genera of the subfamily Zapodinae.
The differences give basis for dividing the subfamily Zapodinae into the three genera Eozapus, Zapus, and Napaeozapus.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "genera" in a variety of sentences. We hope that you will now be able to make sentences using this word.
