Lariosauridce — PJacodon tia . 



53 



mandibular sympliysis is of moderate length and. bears 5 teeth ; 

 the dorsal vertebrae have very short transverse processes. 



Gonchiosaurus is closely allied to NotJiosaurus ; G. davatus Table-case 

 was about one half the size of N. mirahilis. No. 7. 



The genus Mesosaurus, a reptile discovered in the Karoo 

 formation, Griqualand, S. Afi'ica, and since met with in Brazil, 

 is included in the same order with NotJiosaurus. One of the 

 most peculiar features in this genus is the separation of the 

 fourth and fifth tarsalia, so that each metatarsal articulates 



Fig. 72. — Ventral aspect of left pectoral limb Fig. 73. — Ventral aspect of right humerus 



of Mesosaurus tenuidens(J^.GtTya\i),irom of ConchiosoAirus davatus (Meyer); Mus- 



the Karoo System (Trias), Griqualand West chelkalk of Nurnberg (J nat. size); enif, 



(South Africa) \. ent. f., entepicondylar entepicondylar foramen ; a, ectepicondylar 



foramen of humerus; r, radius; u, ulna groove. 

 (see Wall- case No. 8). 



with a distinct tarsale. The centra of the vertebrae have a 

 notochordal canal, and. are small in comparison to the neui*al 

 arches ; while the ribs were anchylosed to the vertebrae, and were 

 of great thickness like those of NotJiosaurus. Abdominal ribs 

 were also present. The skull was much elongated, and furnished 

 with slender recurved teeth, implanted in distinct sockets. 



Order X.— PLACODONTIA (Plate-toothed Reptiles). 



The genus Gyamodus, from the Muschelkalk of Germany, Cyamodus. 

 offers a remarkable modification in its dentition not usually Table-case, 

 met with in the reptilian class, but of which the class of fishes No. 17. 

 affords numerous examples. The skull is as broad as it is 

 long, the greatest breadth being behind, whence the sides 

 converge to an obtuse muzzle. The temporal foss^ are the widest 

 and the zygomatic arches the strongest in the reptilian class, 



