294 



CAPT. D. M. S. WATSON ON SEYMOURIA, 



as to be incapable of ready derivation from an Embolomerous 

 type, while it seems to resemble that or* living Amphibia in 

 being " pseudocentrous," i. e. with the apparent centrum derived 

 from a membranous ossification lying between the notochordal 

 sheath and the cartilaginous blocks of the embryonic vertebra. 

 The animal is of considerable interest as showing that a reptilian 

 type of foot may occur in Amphibia in no way connected with 

 reptilian ancestry. 



Eosauravus. — -The remarkable skeleton from the Coal Measures 

 of Linton named by Williston Eosauravus copei, and described 

 by Cope, Williston, Moodie, and Case, seems to be certainly a 

 Cotylosaur if Case is correct in stating that the " neural arches 

 are low and broad with horizontal zygapophysial faces and short, 

 heavy spines." The " intercentral " position of the ribs, which 

 has troubled certain American authors, really means very little. 

 The skeleton (which I have not seen) is probably not well 

 preserved, and if it be that of a reptile as primitive as Seymouria, 

 no doubt had double-headed ribs of which the capitulum articu- 

 lated with the intercentrum. The slab may have been split so 

 that only this head is preserved. 



The chief interest of the specimen lies in the proportions of 

 the animal. Twenty-three left dorsal ribs are preserved, and the 

 position of the left hand suggests that twenty-eight or more 

 presacral vertebra? were present. There are preserved twenty- 

 three caudals, the latter half of which series shows no signs of 

 tapering, so that the tail may easily have been quite as long 

 as the presacral part of the body. These proportions at once 

 recall the aquatic Embolomeri. Pteroplax has more than 

 28 presacrals, so has Pholidogaster, which animal has a tail as 

 long as its body. The long slender form of Cricotus is familiar 

 from Cope's two skeletons. Thus it is not improbable that 

 Eosauravus retains a primitive form. 



In possessing only two proximal tarsals, it is undoubtedly 

 more advanced than Seymouria. 



Papposaurus. — I have already pointed out that the Lower 

 Carboniferous femur which is the type and only known material 

 of Papposaurus traquari distinctly recalls Seymouria. This 

 resemblance increases the probability (admitted by Williston 

 and Broili) that the form is a reptile. If so, it is by far the 

 earliest known. 



Limnoscelis. — The large Cotylosaur from New Mexico described 

 by Williston as Limnoscelis is in its limb-structure one of the 

 most primitive known. The skull is, however, far more advanced 

 than in Seymouria ; it retains no trace of the typical Eryopine 

 shape of the latter skull, in particular the long slender otic 

 notch of the more primitive form is lost, the posterior surface 

 appearing to be truncated. The occiput unfortunately has not 

 yet been described in detail, but from Prof. Williston's out- 

 line drawing it appears to be derivable from that of Seymouria 

 by a migration downwards of the ends of the paroccipital 



