HISTORICAL REVIEW OF THE PELYCOSAURIA. 7 



Order Dinosauria: Order Theriodontia: Order Anomodontia: 



Section Tretospondylia. Section Binaralia. Family Cryptodontia. 



Genus Tapifiocephahis. Genera Lycosaurus, Genera Theriogtia- 



Vavaily Serratidentia. Tigrisuckus. thus , Kislecephalus . 



Genera Pareisatcriis , Family Mononaralia. V&mWy E7idoihiodoniia. 



Anthodon. Genera Cynodracon, Cyno- Genera Endothiodon. 



suchus, GaUsaurus, Nytho- 

 saurus, Scalaposaiirus, 

 Procolophoti. 

 Family Tecti7iaralia. 

 Genera Gorgo7iops. 



In his Second Contribution to the History of the Vertebrata of the 

 Permian Formation of Texas, p. 39, Cope discussed the relationship of the 

 Pelycosauria to the Mammalia and Batrachia more fully; he says: 



"A not less remarkable characteristic of the Pelycosauria^ as represented by Clepsy- 

 drops and Dimetrodon, is their resemblance to the Batrachia in some important 

 respects. This is seen in the scapular and pelvic arches, which resemble very much 

 those of the Urodela, and of such types as Eryops. The small coossified coracoid 

 only differs from that of Eryops in having two deep sinuses of its free border. The 

 general fonn of the pelvis is similar, but the ilium has a special and peculiar articular 

 face for the sacral diapophysis, which is wanting in Eryops. In the inferior arches, 

 the absence of obturator foramen, and general boat-like form, are the same in both; 

 but in the Pelycosauria the symphysis is not so deep, and the walls less massive. 

 But the resemblance of these arches to those of the Batrachia in question is greater 

 than to those of any order of reptiles. 



"Another point of resemblance to the Batrachia is seen in the humerus. In my 

 previous essay on the Pelycosauria above cited, I defined six types of humerus as 

 occurring in the Texas Permian. Two of these were described as wanting the fora- 

 men, while the others were stated to possess it; other differences between these types 

 exist, but they were not mentioned. Since then Gaudray has added a third form to 

 the former group, which he has ascribed to a reptile under the name of Eiichiro- 

 saurus. I have detected this fonn in my Texas collections together with another, 

 which has no condyles at either extremity. Thus eight forms of humerus are found 

 in this formation. 



"That the type with the supracondylar foramen belongs to the Pelycosauria has 

 been satisfactorily shown by its presence in the skeleton of Clepsydrops natalis and 

 in Cynodraco major, where Owen first identified it. I find the type without this 

 foramen frequently associated with the skeletons of Eryops and other Stegocephali. 

 There is no other element that can be regarded as the humerus of this type. It more- 

 over has distinct points of resemblance to the humerus of existing Batrachia, parallel 

 with similarity' traceable in the femora of the extinct and recent genera. There is 

 then every reason for believing that we have in the humerus oi Eryops and its allies, 

 an element which approaches closely in its characters to that of the Pelycosauria, and 

 hence to that of the Moiiotremata. 



