178 



REPTILIA 



CLASS III 



head and short neck. Skull depressed and narrow, attaining a length of 

 1*3 m. Internal nares remotely situated, mandibular symphysis considerably 



extended. Margin of upper jaw on either side with a series 

 of about thirty powerful carinated teeth, sometimes 25 cm. 

 long ; the crown traversed for a portion of its height by 

 strong elevated ridges. About twenty very short cervicals 

 with double-headed ribs. Limb girdles similar to those of 

 Plesiosaurus. Lias to Upper Jura ; England, Northern France, 

 Switzerland, Bavaria, Russia, and India. 



Megalneusaurus } Knight. Largest known Plesiosaur, the 

 humerus attaining a length of 1 m., or about one-half the 

 length of the entire fore-limb, and articulating only with 

 the radius and ulna. The latter bones are polygonal and 

 closely applied against each other and the three proximal 

 carpals. Coracoids produced in front of the glenoid cavity ; 

 vertebrae elongated. Upper Jura ; Wyoming. M. rex, 

 Knight. 



Elasmosaurus, Cope (Fig. 282). A skeleton in Philadelphia 

 lacking the head exceeds 13 m. in length. The seventy-two 

 cervicals are longer than deep, and bear short, single-headed 

 ribs. The neural arches are all fused with their centra, but 

 the chevron bones are articulated with the caudals. Pectoral 

 arch similar to that of Oryptoclidus. Limbs and greater part 

 of the skull unknown. Upper Cretaceous ; Kansas. 



Dolichorhynchus, Willist. Head long, snout very slender ; 

 mandibular symphysis much elongated; teeth small, numerous; 

 vomers very long ; posterior nares small, included between 

 vomer and pala- 



FiG. 281. 

 Plioscmrus grandi 



Owen. 

 gian ; 

 Tooth, 

 Owen). 



tines ; 

 niina : 



Kimmerid- 



Dorsetshire. 

 i/ 4 (after 



no posterior palatine fora- 

 pterygoids contiguous only 

 at extremities. Neck shorter than 

 head ; cervical ribs single-headed ; 

 axis with ribs ; nineteen cervicals 

 and about thirty dorsals are pre- 

 sent ; tail very short, conical. 

 Clavicular arch complete, the 

 clavicles articulating with the long 

 precoracoidal process. Ischium 

 elongate. Humerus and femur 

 moderately expanded ; three pro- 

 podials. Known by a nearly com- 

 plete skeleton about 3 m. in length 

 from the Niobrara Cretaceous of 

 Kansas. 



Polyptychodon, Owen (Fig. 283). 

 Imperfectly known, teeth resembling those of Pliosaurus, but with more 

 prominent coronal ridges, some of which extend to the apex. Middle and 

 Upper Cretaceous ; England, Germany, and Russia. 



Fig. 282. 



Elasmosaurus platyurus, Cope. 

 Upper Cretaceous ; Kansas. 

 Pectoral arch, shaded parts 

 restored ; greatly reduced, cor, 

 Coracoid ; so, Scapula (after 

 Cope). 



Fig. -283. 



Polyptychodon inter- 

 ruptus, Owen. Ceno- 

 manian ; Kelheim 

 Bavaria. Tooth, 1 /j. 



