2 86 PROKEPTILIA 



CHAP, 



Until more genera are better known than they are now, it is 

 premature to divide the present sub-class into orders. 



Eryo2^s, with several species in Texas and New Mexico. E. 

 megacephalus is the most abundant and the largest species, its 

 broad and flattened skull measuring more than 1 8 inches in length 

 and 12 in width. A\^ith the exception of the nostrils and the 

 small orbits, the skull is entirely encased in bone, with a rough, 

 pitted surface, but without any distinguishable sutures. The 

 absence of mucous canals, so common in the Stegocephali, is 

 worthy of note. The quadrates extend obliquely outwards and 

 backwards, so that the joint with the mandible lies in a plane 

 behind the occiput. The mandibles are devoid of a projecting 



angular process. The teeth are numerous, 

 small, and pointed. The vertebrae are 

 typically temnospondylous, consisting each 

 of three pairs of separately ossified pieces, 

 which, although closely packed together. 

 Fig. 57.— Trunk vertebrae of are not suturally connected. The neural 

 Eryops (ct ¥\g. 56, 4, p. arclics possess high spinous processes, thev 



283). CJJ, Articular fai;et ■ ^ ^ ^ ^ ^ ' j 



of the capituiuin of a rib. articulate by sliort and broad zygapo- 



physes and are, with their triangular 

 bases, wedged in between the two ventral pieces, the posterior of 

 which (the united interventralia) is in broader contact with the 

 neural arch and lies behind it ; the anterior piece (the united 

 basiventrals) appear as typical, but large, intercentra, and bear on 

 their posterior, dorsal margin the facets for the ribs. The latter 

 are short, but are broad at their proximal ends, which are not 

 bifurcated ; they extend their articulation from the " intercentra " 

 upon the short lateral processes of the neural arches. The tail is 

 short and ends in a pointed coccyx, owing to fusion of the last 

 vertebrae. 



The pubes and ischia are heavy, the former flattened and 

 broadened out. The limbs are of an almost ideal pentadactyloid 

 type ; strongly developed for terrestrial locomotion. The ulna 

 possesses a large olecranon. The carpus consists of ten separate 

 pieces, ulnare, intermedium, radiale, two centralia and five distal 

 carpalia. The latter support only four metacarpals and fingers, 

 the second finger being completely abolished, an explanation 

 suggested by Cope and corroborated by Emery.^ 



' Anat. Anz. .\ix. 1897, p. 201. 



