677 



SAURIA. 



SAURIA. 



673 



serrated margins ; but its breadth is much greater than its length ; 

 this they ascribe to a species which they name P. platyodon; the other 

 they refer to a species designated by them P. cylindrodon. 



The genus Cladeiodon (Owen) derives great interest from having 

 been found in the same quarries of New Red-Sandstone (Keuper ?) at 

 Warwick and Leamington a? contained the remains of Labyrinthodon. 

 " In their compressed form," says Professor Owen, " anterior and 

 posterior serrated edges, sharp points, and microscopic structure, 

 these teeth agree with those of the Saurian reptiles of the Bristol 

 conglomerate. In their breadth, as compared with their length and 

 thickness, they are intermediate between the Tliecodontosaurus and the 

 Palaoiaurui platyodon ; they are also larger and more recurved, and 

 thus more nearly approach the form characteristic of the teeth of the 

 Meyaloiaurus. From these teeth however they differ in their greater 

 degree of compression, and in a slight contraction of the base of the 

 crown. I propose therefore to indicate the genus, of which, as yet, 

 only the teeth are known, by the name of Cladeiodon, and for the 

 species from the Warwickshire sandstone the name of 0. Lloydii, in 

 testimony of the friendly aid of Dr. Lloyd of Leamington, to whose 

 exertions I owe the materials for the description of the teeth of the 

 present genus, and the still more remarkable ones of the British 

 species of Labyrinthodon, with which the teeth of the Cladeiodon are 

 associated." 



Professor Owen retains the name of Protorosaurus for the small 

 species of Saurian found in the pyritic schists of Thuringia, which, he 

 observes, like the dolomitic breccia near Bristol, rank as the oldest 

 member of the new red -sandstone. He adds in a note, that besides 

 the Thecodont type of dentition the Protorosaurus differs from all 

 recent Saurians, and resembles the Pterodactyle in the great relative 

 size of the cervical vertebra} and the ossified tendons of the muscles 

 of that region of the spine ; it differs from all reptiles, except the 

 extinct Rachieotaurui, in the bifurcate superior spines of the caudal 

 vertebra:. 



In the extinct Saurian from the Oolitic Formation at Neuffen in 

 Wiirtemberg (Thaumatosaurus oolithicus, Meyer), Professor Owen found 

 the teeth conical, slightly curved, straighter on the inner side of the 

 crown, and implanted by a long and strong root, rather obliquely, in 

 a deep socket The base and basal portion of the crown presented a 

 nearly circular transverse section, and the wide pnlp-cavity in this 

 part of the tooth exhibited an elliptical transverse contour ; the tooth 

 becomes slightly compressed towards the apex. Its implanted base 

 is stated to be the broadest part of the tooth ; the breadth of the 

 crown to its height is as one to three; the crown, is described as 

 invested with a thin layer of enamel, the basal half of which is marked 

 by longitudinal stria! ; these stria: seemed to consist of folds of the 

 enamel, which do not extend into the dentine. The successional 

 teeth are noticed as penetrating into the interior of the fixed teeth in 

 the progress of their development. 



The teeth of Itchyrodon, a gigantic reptile from the Jura Lime- 

 stone of the Canton of Aargau, are described as somewhat resembling 

 those of the Thaumutosaurus, but the external longitudinal stria; of 

 the crown of the tooth as being sharper and more elevated, and the 

 enamel between the stria) as roughened by irregular linear risings ; 

 whilst the teeth of the Pacilopleuron, an extinct reptile, also of 

 gigantic dimensions, from the Oolitic Beds at Caen, has, according to 

 the single tooth referred to that species, a more compressed crown 

 than the teeth of Tkaumatoiaurus ; the stria! are also described as 

 wider apart, and the two diametral ones as developed into ridges 

 which extend to the apex of the tooth. 



In noticing the teeth of the Enaliosaurians, Professor Owen observes 

 that those of the Ichthyosauri [ICHTHYOSAURUS] have a simple, more 

 or less acutely conical form, with a long and usually expanded or 

 ventricose base or implanted fang, and that they are confined to the 

 intermaxillary, maxillary, and premandibular bones, in which they are 

 arranged in a pretty close and uninterrupted series, and are nearly of 

 equal size. They consist, he informs us, of a body of unvascular 

 dentine, invested at the base by a thick layer of cement, and at the 

 crown by a layer of enamel, which is itself covered by a very thin 

 coat of cement; the pulp-cavity is more or less occupied, in fully- 

 formed teeth, by a coarse bone. He observes that the external surface 

 of the tooth is marked by longitudinal impressions and ridges, but 

 the teeth vary both as to outward sculpture and general form in the 

 different species. 



" The chief peculiarity," he says, " of the dental system of the 

 Ichthyosauri is the mode of implantation of the teeth. Instead of 

 being auchylosed to the bottom and side of a continuous shallow 

 groove, as in most Lacertians, or implanted in distinct sockets, as in 

 the Thecodon, Megalosaur, or Pterodactyle, they are lodged loosely in 

 a long and deep continuous furrow, and retained by slight ridges, 

 extending between the toetli, along the aides and bottom of the 

 furrow, and by the gum and the organised membranes continued 

 into the groove and upon the base of the teeth. The germs of the new 

 teeth are developed at the inner side of the base of the old ones." 



The chief distinction offered by the dental system between the 

 Ichthyosauri and Pleiioiauri is pointed out by Professor Owen as 

 existing in the loose implantation of the teeth of the latter in separate 

 alveoli. In this deviation from those of the Ichthyosaur, the Plesio- 

 ranr, observes the Professor, approximates to the crocodilian type, 



and this affinity, he adds, is likewise manifested in the unequal size 

 of the teeth, and the development of some of the anterior ones into 

 large tusks. They are described as being composed, like those of the 

 Ichthyosaur, of a body of hard and simple dentine, covered at the 

 crown by a coat of enamel, find at the base by a coat of cement ; but 

 the latter is relatively thinner than in Ichthyosaurus, and ia not 

 inflected into the substance of the dentine. 



Professor Owen proposes the subgeneric name of Pleiosaurus for 

 a gigantic extinct reptile whose remains have been found in the Kim- 

 meridge Clay. The teeth are described as differing from those of 

 Plesiosaurus in their greater relative thickness as compared with their 

 length, and in the subtrihedral shape of their crown. The outer side 

 is slightly convex, sometimes nearly flat ; it is separated from the 

 two other facets by two sharp ridges ; these are more convex, and 

 the angle dividing them is often so rounded off, that they form a 

 demi-cone, and the shape of the tooth thus approximates very closely 

 to that of Mosasaurus, with which it is equal in size, but from which 

 it is readily distinguished even when the crown only is preserved, by 

 the ridges which traverse the inner or convex sides ; the outer flat- 

 tened surface alone being smooth. The long fang of the perfect 

 tooth at once removes it from the Acrodonts, and allies it with the 

 Thecodonts, among which it approaches nearest, in the superficial 

 markings of the crown, to Plesiosaurus. The vertebra! of the neck 

 are so modified that the peculiarly elongated proportion of this part 

 of the spine, which characterises the typical Plesiosauri, is exchanged 

 for one that much more nearly approaches the opposite condition of 

 the cervical region in the Ichthyosauri ; thus presenting an abrogation 

 of the main characteristic of the Plesiosauri combined with the mora 

 crocodilian proportions of the teeth of this Pleriosaurus, of which a 

 fine specimen (Plesiosaurua brachydeirut, Owen) from Market-Raisin 

 is preserved in Dr. Buckland's collection at Oxford, consisting of 

 considerable portions of the upper and lower jaws. 



We now have to examine the other parts of the skeleton of the 

 Sauriaus. That of the Enaliosaurians is noticed in the articles 

 ICHTHYOSAURUS and PLESIOSAURUS; that of the Crocodilians, under 

 the article CROCODILID.E. Among these animals there is a wonderful 

 adaptation of the structure to their modes of progression and habits 

 of life. In the extinct Pterodactyle, we have, more especially in the 

 anterior extremities, a modification in the development of the bones, 

 to enable the animal to move through the air with a true flight. 

 [PTERODACTYLE.] In the great mass of the terrestrial Saurians, the 

 bones of the extremities are elongated, to facilitate progression on the 

 earth, on trees, or even, as in the case of the Geckos, on smooth walls 

 and ceilings. When we come to the aquatic groups, we have in the 

 Crocodilians a more compact form of the bones of the hand and foot, 

 but still adapted to occasional progression on land, till at last, in the 

 Enaliosaurians, the short, compact, and compressed bones of the 

 extremities become mere paddles to row the body through the water, 

 like those of the tortoises among the reptiles, and of the seals and 

 whales (in the latter as far as the anterior extremities are concerned) 

 among the mammiferous animals 



Cuvier remarks that the study of the vetebree of the living Saurians 

 is highly necessary, in order to a recognition of the numerous fossil 

 bones belonging to this family, and he thus proceeds to describe thoae 

 of the former : The atlas of the Monitor is a ring composed of 

 three pieces two upper ones, united to each other at the dorsal part, 

 notched in front and behind for the nerves, and one lower piece. The 

 anterior surface of the axis (dentata), or rather of that portion of it 

 which is analogous to the odontoid, penetrates in the ring of the atlas 

 and fills nearly half its width, leaving always in front a concavity for 

 the condyle of the head. Below, on the junction of the atlas, of the 

 odontoid, and of the body of the axis, is a triangular piece which 

 gives off a pointed hook directed backwards. The axis is compressed ; 

 its annular part takes, above, the form of a longitudinal pointed crest ; 

 its anterior articular facets have their plane turned outwards ; the 

 posterior ones have them downwards ; the body terminates in a trans- 

 verse convexity of a kidney shape ; on each of its lateral surfaces is a 

 small and but slightly projecting crest, which has, towards its anterior 

 third, a small point ; below, there is a crest, under the posterior part, 

 which is enlarged backwards. The sutures which distinguish the 

 annular part of the body are soon effaced ; but for a long period a 

 small epiphysis may be seen at the posterior point of each of the two 

 crests. The five succeeding vertebras reaemble the axis, excepting 

 that they are without an odontoid ; but their anterior surface has a 

 concavity proportioned to the convexity of the preceding vetebra, 

 their dorsal or spinous crest or process is elevated and shorter, and 

 their transverse processes enlarge slightly, and present a convex facet 

 for the support of the cervical rib. The lower crest exists ; and this 

 is what distinguishes the cervical from the dorsal vertebrae, tbe body 

 of which last is even below, with the exception of the throe first, 

 which have each a tubercle becoming gradually less and less. At the 

 point of these crests is an epiphysis, which in the other sub-genera 

 forms the crest by itself. The dorsal vertebra! after the twelfth have 

 always a squared spinous process, an anterior concave and a posterior 

 surface, both of a kidney-shape, horizontal articular apophyses, the 

 posterior looking downwards, the anterior upwards ; and on each side 

 under the anterior apophysis, by way of a transverse apophysis, a 

 vertical oval-shaped tubercle for supporting the rib. The number of 



