The suborder Rhinae includes those sharks having the vertebrae tectospondylous, that is, with two or more series of calcified lamellae, as on the rays.
In the chimaeras (Holocephali) the notochord persists and is surrounded by a series of calcified rings.
Echinoderma with the viscera enclosed in a calcified and plated theca, of which the oral surface is uppermost, and which is usually attached, either temporarily or permanently, by the aboral surface.
Associated with various forms of Ammonoids there have been found peculiar horny or calcified plates, sometimes contained within the body-chamber of the shell, sometimes wholly detached.
In the Oigopsida the shell is represented by a proostracum which is no longer calcified by forms a chitinous plume or gladuius, and a similar rudiment occurs in Loliginidac (fig.
The jaws have the form of powerful beaks, either horny or calcified (Nautilus), and are capable of inflicting severe wounds.
But this proper calcified wall is quite distinct from calcareous tubes surrounding the siphuncle, which are developed from the septa.
Under tin, teeth are calcified and saved by the deposit of lime-salts from the contents of the dentinal tubuli.
As long as growth continues the outer layers of this pulp become successively calcified and added to the substance of the dentine.
Bony plates are sometimes present, as in the Siluridae, or the body may be encased in a complete armour of calcified plates, as in Ostracion.
The cartilage may be hyaline, as in the omosternum and xiphisternum, or may be more or less calcified as in part of the suprascapula and the epiphyses of the limb bones.
These are small, pointed, calcified structures arranged in large groups on the premaxillae, mandible, vomer, and superior and inferior pharyngeal bones.
The distal row of tarsals consists of three very small pieces of calcified cartilage.
It bears attached to its posterior end a broad somewhat bilobed plate of partiallycalcified cartilage, the =xiphisternum= (fig.
The parts left unshaded are ossified; those marked with small dots consist of hyaline cartilage, those marked with large dots of calcified cartilage.
The endoskeleton of the dogfish consists almost entirely of cartilage, which however may become calcified in places, e.
The skull is well calcified and the auditory capsules are specially large.
Often the cartilage becomes calcified in places, as in the vertebral centra of Scyllium and other Elasmobranchs.
Calcified teeth representing the milk dentition occur in the foetus, but the teeth are never functional, and always disappear before the close of foetal life.
Interspersed among these areas are irregularly shaped clean-cut ulcers having as a rule a smooth base, and frequently on the base is a thin plate of calcified matter.
Numerous calcified plaques, thickening and curling of the aortic valves, giving rise to insufficiency of the aortic valves.
More frequently there are rings of calcified material placed closely together or irregular beading, giving to the palpating finger the impression of feeling a string of very fine beads.
Persons with calcified arteries may be perfectly comfortable, while those with only moderate thickening may have many severe symptoms.
Cases of the most extreme grade of pipe stem arteries are, however, seen in old women, and calcified arteries are not hard to find among the inmates of an old woman's home.
There were no changes in the ascending aorta but in the descending portion there were scattered nodules and smallcalcified plaques.
Many puny individuals with stiff, calcified arteries go about with more ease than a robust man with thickened arteries only.
If these plates are a calcified muco-cartilage, then the whole argument for their ancestry from animals with a cartilaginous skeleton falls to the ground, for muco-cartilage is the precursor not only of bone, but also of cartilage itself.
The distinctive characteristic of rickets is the broad area of osteoid tissue which is formed at the epiphyseal junction, a broad band of incompletely calcified cartilage not found in scurvy.
Now and then these grains are found to be in a calcified condition.
Sometimes, also, there are found at the post-mortem examination of animals which have not reacted small fibrous or calcified lesions in such a condition that one is tempted to believe them cured.
The positions of the primordial valves, and the direction of growth in the calcified valves, are, in all the species, the same as in Lepas.
The exterior yellow membrane is marked, or rather composed of successive narrow rims, which, in fact, are the lines of termination of the laminae of membrane, which in a calcified state form the cup itself.
The basal margin is internally strengthened by a calcified rim, more or less developed.
Primordial valves very plain, with the usual hexagonal structure: those of the terga, rounded at both ends, instead of being square, as in the mature calcified valves.
I was not able to make out quite certainly whether the two segments are continuously united at their umbones by a non-calcified portion of valve, as is certainly the case with Dichelaspis.
Valves minute, thin, generally more or less linear, placed far distant from each other; sometimes imperfectly calcified and covered by chitine membrane, or imbedded in it.
The membrane of the peduncle is continuous with the yellow membrane coating the external surface of the cup; and this latter membrane is continuous with those delicate laminae which, in a calcified condition, form the layers of the cup itself.
Peduncle, only small fragments are preserved; the calcified scales are small, closely imbricated, several of them together only equalling in length the basal margin of the rostral latera.
In the case of an extremely calcified membrane which apparently cannot vibrate.
The most striking feature is the softness (malacia) of the bones, due to excessive absorption of osseous tissue, and the formation of an imperfectly calcifiedtissue at the sites of ossification.
The osteoid sarcoma is characterised by the formation of a tissue resembling bone but deficient in lime salts, and the petrifying sarcoma by the formation of calcified areas in the stroma.
The room would be taken up by thecalcified plates, and when the latter disappeared, as they have in the vast majority of existing Whales, the naked skin alone would be left.
Moreover, in the Indian Neomeris, a close ally of the Porpoise, a more abundant calcified covering of scales exists along the whole back of the animal.
Most of them are covered with a calcified skin, as in the case of crabs and lobsters; but many are protected with a chitinous or horny covering such as we observe in shrimps and prawns.
This lid is called the operculum, and is constructed of a horny material, often more or less calcified on the exterior, and is attached to the hinder part of the foot.
The dense calcifiedsubstance of which teeth are largely composed.
The intensely hard calcified tissue entering into the composition of teeth.
I have only further to remark, that the sutures, though very strongly united, are not calcified together; for they easily separate after the action of caustic potash.
In some specimens the scuta and terga are partially calcified together.
I have seen, are calcified together, with no trace of a suture.
Kingii the terga and scuta are firmly calcified together.
Shell moderately convex, nearly smooth: scutum and tergum calcified together without any suture: scutum furnished with a small occludent ledge, with the adductor ridge descending below the basal margin: tergum square without a spur.
La Plata, the walls had likewise grown rectangularly inwards, forming a flat base, and had then turned upwards in the middle, forming a medial crest, with the edges not quite calcified together.
Hameri and crenatus, separate on a touch; in others, they adhere so strongly as to prove that the sutures must be calcified together.
The scuta and terga are calcified together by their apices.
The scuta and terga, in all the specimens which I have seen, were firmly calcified together; in some, a trace of a suture could be seen externally, but hardly a trace internally.
Varieties With the Scuta and Terga Calcified Together.
In one specimen, in which both the shell and operculum had undergone much disintegration, the scuta and terga were calcified together.
This calcified cartilage then undergoes absorption-- it must not be imagined for a moment that bone is calcified cartilage.
Posteriorly the vertebral column terminates in the urostyle, a calcified unsegmented rod.
Its upper end, adjoining the quadrate region, becomes calcified and then absorbed, and its lower, with the exception of the extreme point, is ossified and subsequently incorporated in the dentary.
In most Teleostei the enamel and dentine layers have disappeared, and the scales are entirely formed of a peculiar calcified tissue developed in the dermis.
Tissues which may become calcified are, in the first instance, the connective tissues, and of these fibrous tissue and cartilage are especially liable.
The common feature in the aortic changes and in the calcified muscular coat is the element of age.
The calcification of certain tumors, as the fibro-myoma of the uterus, is equally sanatory, the further growth of the calcified parts being thus checked.
A calcified thrombus may be intimately united to the vascular wall, the results of calcification and organization being associated.
The sacral diapophyses are expanded and have a border of calcified cartilage laterally.
The scapula is flat and expanded dorsally; the suprascapula is broad, flat, and calcified in large adults.
In the flat valve there is a large oblong hole just under the apex, through which projects a calcified byssus, by means of which the animal secures itself to oysters, dead shells, stones, or any solid object.
It has the same sort of calcified byssus as /Anomia/, and also the hole to accommodate it in the smaller valve.
