1895.] ^^'^ [Cope. 



Pariasaurus and Pariotichus, but not in Elginia or Empedias. A charac- 

 ter of the American genera is tlie weakness of the attachment of the basi- 

 occipital to the sphenoid. The basioccipital is h)st from the only linovvn 

 specimen of Elginia, and the sphenoid projects freely below it in Paria- 

 saurus. The roof of the mouth in this order is a good deal like that of the 

 Lacertilia, lacking the palatine foramen. 



Tlie order Cotylosauria was defined by me in the American Naturalist 

 for 1880, p. 304, and in 1889 (October). In 1889 (Transac. of the Roy. 

 Sac. London, p. 392), Prof. Seeley gave it the name of Pariasauria. In 

 my Syllabus of Lectures on Vertebrate Paleontology (1891, p. 38), I 

 arranged the group as a suborder of the Theromora. In 1893 ( Trans. 

 Amer. Pliilos. 8oc., p. 13, PI. i), I again regarded the Cotylosauria as 

 an order, and desciibed the characters of the skull in three of the genera, 

 and gave figures of them. 



Seeley has objected to the reference of the genera Pariasaurus and 

 Empedias to the same order, on the ground that the elements connecting 

 the supraoccipital and the quadrate rest on the occipital elements in the 

 latter, while they are elevated above them in the former. This character 

 would not, however, define orders, as both conditions arc found in the 

 Lacertilia; but might distinguish families within an order. However, 

 Seeley 's description and figure of the occipital region in Pariasaurus 

 bainii* sliow that the structure only differs from that of the Diadectidse 

 in the presence of a large foramen between the supraoccipital and exoc- 

 cipital bones on each side. 



Seeley has also proposed to include Eryops in this order. But Eryops 

 is a true batrachian with two occipital condyles, and a large parasphe- 

 uoid bone. The dental structure is like that of Actinodon, and the ver- 

 tebrsB are of the rhachitomous type, which is unknown among Reptilia. 



The known species of the Cotylosauria range in dimensions from that 

 of the South American Caimans (Chilonyx, Pariasaurus sp.) to that of 

 the smaller Lacertilia, e. g., Eumeces quinquelineatus (Isodectes and Pario- 

 tichus sp.). They range from the Permian to the Trias, inclusive, and 

 have been found in South Africa, North America and Scotland. 



This order embraces at present four families, which are distinguished 

 as follows : 



I. Teeth in a single series. 

 Teeth not transversely expanded ; vertebral centra with surf\ices only 



ossified ; no hyposphen ElginiidcB. 



Teeth not transversely expanded ; vertebral centra ossified ; no hypo- 

 sphen Pariasauridm. 



Teeth with the crowns transverse to the axis of the jaws ; vertebrae ossi- 

 fied and with a hyposphen-hypantrum articulation Diadectidce. 



IT. Teeth in more than one series in (one or) both jaws. 

 Teeth with cylindric roots ; vertebrae ossified ParioticMdce. 



* Philos. Trans. Roy. Soc, 1892, p. 326, PI. 18, Fig. 2. 



FKOC. AMER. PHILOS. SOC. XXXIV. 149. 8 D. PRINTED FEB. 8, 1896. 



