April 9, 1897.] 



SCIENCE. 



593 



The sub-order Pelycosauria was established 

 by Professor Cope in May, 1878, for certain 

 Reptilia, especially Clepsydrops and Dimetrodon, 

 from the Permian of Texas. It was said to 

 differ from the Rhynchocephalia by the absence 

 of the quadrato-jugal arch. At the end of the 

 same year the order Theromorphas was estab- 

 lished, as distinct from the Hhynchocephalia, con- 

 taining the suborders Pelycosauria and Anomo- 

 dontia (Owen). 



The characters of this order with its two sub- 

 orders were given as follows: 



Theromorpha, Cope. Scapular arch consisting 

 at least of scapula, coracoid and epicoracoid 

 which are closely united. Pelvic arch consist- 

 ing of the usual three elements, which are 

 united throughout, closing the obturator fora- 

 men and acetabulum. Limbs with the phalanges 

 as in the ambulatory types. Quadrate bone 

 proximally united by suture with the adjacent 

 elements. No quadrato-jugal arch. 



Pelycosauria. Two or three sacral vertebrse ; 

 centra notochordal; intercentra usually present. 

 Dentition full. 



Anomodontia. Four or five sacral vertebrse ; 

 centra not notochordal; no intercentra. Denti- 

 tion very imperfect or wanting. 



The order Theromorpha was regarded by Pro- 

 fessor Cope as approximating the Mammalia 

 more closely than any other division of the 

 Reptilia, and as probably the ancestral group 

 from which the latter were derived. 



The order Theromora has been admitted by 

 nearly all paleontologists and zoologists, and 

 the opinion of the close relationship of this 

 group with the Mammalia has found very many 

 supporters. 



This view is not correct. It is shown [that 

 the order Theromora has no existence. The 

 Pelycosauria cannot be brought together with 

 the Anomodontia, since they have both the 

 upper (postorbito-squamosal) and lower (quad- 

 rato-jugal) arches, like the Rhynchocephalia. 



This result was reached by the study of an 

 excellent specimen of Dimetrodon incisivus, Cope, 

 collected in the spring of 1896, by Dr. E. C. 

 Case, while in charge of the field expedition of 

 the department of paleontology of the Univer- 

 sity of Chicago. 



The following conclusions were reached, after 



the description of the skull and the principal 



portions of the skeleton: 



The Affinities of the Pelycosauria. 



There cannot be any doubt that Dimetrodon 

 is nearest to the Bhynchocephalia and Progano- 

 sauria (Paleeohatteriidse). The structure of the 

 skull, the vertebral column, and the humerus 

 are of the same type. 



The specialization of the Pelycosauria consists 

 in the enormous development of the neural 

 spines of the dorsal vertebrse, and in the reduc- 

 tion of the upper part of the quadrate and its 

 nearly complete inclosure by the squamosal, 

 prosquamosal and quadrato-jugal. It is quite 

 evident that the Pelycosauria with the two temporal 

 arches, and the specialized neural spines cannot he 

 the ancestors of mammals; they represent a 

 specialized side branch of a line leading from 

 the Proganosauria to the Rhynchocephalia, 

 which becomes extinct in the Permian. 



The mammals have a single temporal (zygo- 

 matic) arch ; the posterior nares are placed far 

 back, and are roofed over the maxillary and 

 palatine plates ; the quadrate is completely co- 

 ossified with the squamosal and quadrato-jugal ; 

 the occipital condyle is double, the entepicon- 

 dylar foramen is present in all the generalized 

 forms. The ancestors of mammals must show 

 the same condition. 



Seeley has combined a number of Permio- 

 Triassic Reptilia from South Africa into an order 

 which he calls Oomphodontia. These reptiles 

 are : Tritylodon, Owen (always so far considered 

 a mammal); Diademodon, Seeley; Gomphognathus, 

 Seeley; Micro gomphodon, Seeley; and Triracho- 

 don, Seeley. 



In Gomphognathus we have a double occipital 

 condyle ; the posterior nares are placed far back 

 and are roofed over by the maxillary and ptery- 

 goid plates, and there is an entepicondylar 

 foramen. The quadrate seems to be of the re- 

 duced form ; a condition we see also in the 

 closely related Cynognathus. 



These forms look very much like mammals 

 and could possibly be ancestral to them. We 

 must suppose that the condition of the palate 

 seen in the Mammalia and Gomphodoniia has 

 been developed from a type which we find 

 among the Rhynchocephalia. The Crocodilia, 

 where we have a palate similar to that of mam- 



