1S92.] 27 J [Cope. 



the coracoid element is of reduced size, and is coossified witli the scapula. 

 In both (except Cotylosauria) the capitular articulation of the ribs is in- 

 tercentral. In both, the humerus has distal condyles and epicondylcs, 

 and there is an entepicondylar foramen in the Pelycosauria as in the 

 lower Mammalia. The posterior foot is constructed in the Pel,ycosauria 

 almost exactly like that of the Prototheria. The single occipital condyle 

 of the reptiles is not found in the Mammalia, but in some of the Lacertilia 

 (Uroplates, Gecco) there are two condyles, the median (basioccipital) 

 portion of the single condyle being rudiraenlal. The Pelycosauria could 

 not, however, have given origin to the Prototheria, since in that sub- 

 class of mammals there is a well-developed coracoid. But in the Proco- 

 lophonina this element is developed as in the Prototheria. Moreover, 

 the Pelj'cosauria and the Procolophonina have the interclavicle, which 

 is an element of membranous origin, while in the Prototheria we have 

 the corresponding cartilage bone, the episternum. This element is pres- 

 ent in the Permian order of the Cotylosauria, which is nearly related 

 to the Pelycosauria. This order has, however, single-headed ribs, spring- 

 ing from the diapophyses, which is not usual in the Mammalia. But 

 in some Cotylosauria the diapophyses are short, and in the Monotre- 

 mata the postcervical ribs are single-headed, so this character may not 

 prove an insurmountable one. It is evident that the Mammalia were 

 derived from some type probably referable to a Permian reptilian order 

 of the Theromorous series, although to which one is not yet known. 



The Reptilia have been supposed by Hseckel to have taken their origin 

 from the Batrachia. I have indicated that it is probable that the 

 Batrachiau order, which stands in this relation to the Reptilia, is the Em- 

 bolomeri of the Permian epoch. This conclusion rests on the following 

 considerations. The Reptilian order of the Cotylosauria approaches the 

 Batrachia of the subclass Stegocephali in the overrooflng of the pos- 

 terior regions of the skull ;. in the presence of vomerine teeth, and in the 

 absence of obturator foramen of the pelvis. In some Cotylosauria (Dia- 

 dectidoe) the stegocephalian intercalary bone of the skull is well devel- 

 oped. But in the Cotylosauria, the vertebral column consists mainly of 

 centra, while in the Stegocephali it consists entirely or partly of inter- 

 centra. But in the Embolomeri the centra are well developed, and are 

 larger than the intercentra anterior to the pelvis. Hence this is the only 

 order of Stegocephali from which the Reptilia could have been derived. 



Hajckel derived the Batrachia from the Dipnoi (Dipneusta), and I fol- 

 lowed him in this belief, being strengthened in it by Huxley's ascription 

 of an autostylic suspensorium of the mandible* to both divisions. This 

 phylogeny is questioned by Pollard f and by Kingsley $ who would see 

 the ancestry of the Batrachia in the Crossopterygian fishes on erabryologi- 

 cal grounds derived from a study of Polypterus. In support of their 



* Proceedings Zoologicat Society of London, 1876, p. 59. 

 t Anatomischer Anzeiger, vi, p. 338, 1891. 



t American Naturalist, 1892, p. 679. Kingsley would also derive the Dipnoi from 

 Crossopterygia. 



