58 REVISION OF THE PELYCOSAURIA. 



Ctenosaiirjis ein letzter Nachziigler der bisber nur aus deui Perm bekannten Familie 

 der Clepsydropiden ist. Ein solcbes Vorkommen ist zur VervoUstaudigung der triassi- 

 scben Landfauiia hocbst interessant." 



The position of the form is uncertain, occuiring as it does, widely 

 removed, both geologically and geographically from other members of the 

 group. The evidence is very meager upon which to assert the persistence 

 of the suborder into a higher formation. It is probably a persistent member 

 of the Pelycosauria^ but may be a case of parallelism in some other group. 



Subfamily NAOSAURINAE nov. 



(i) Vertebral spines with lateral processes. 



(2) Bottom line of anterior dorsal and posterior lumbars not greatly shortened. 



(3) Cervicals smaller than anterior dorsals. 



(4) Crest of ilium vertical and widely flared. 



(5) Dorsal ribs with tuberculum reduced to a tuberosity on edge of rib. 



Genus NAOSAURUS Cope. 



Am. Nat., vol. xx, 1886, p. 544. 

 Am. Nat., vol. xii, 1878, p. 319. 

 Proc. Am. Phil. Soc, vol. x:v, 1878, p. 44. 



Type : Naosaiinis cruciger. A mixed lot of bones containing several imperfect 

 centra and several incomplete spines held in their natural position by the matrix. 

 No. 4003 Am. Mus. Nat. Hist, Cope, coll.; valley of the L,ittle Wichita river, Texas. 



Original desa-iption : The specimen was originally described as a species of 

 Dimetrodoii in 1878 and 1880, see N. claviger. The original description of the 

 genus separating it from Dinietrodon was as follows: "Spines not quite so elevated 

 as in the Dinietrodon incisiviis ; but are more robust, and have transverse processes 

 or branches which resemble the yard-arms of a ship's mast." 



Cope later described the skull of A^. claviger as characteristic of the 

 genus Naosaurus. He regarded it as at least very similar to that of Dime- 

 trodon^ for he remarks, ''''Naosaurus differs from Dinietrodon only in the 

 presence of transverse processes on the neural spines." The desciiption 

 of the skull is given in the description of N. claviger below, but it is 

 a very curious fact that neither by relation of bones nor by any record 

 of number or label is there any considerable fragment of a skull unmistak- 

 ably connected with spines of Naosaurus, either in the New York or the 

 Chicago collections. Two skulls are labeled by Cope as N. claviger and 

 TV. cruciger, but there is to-day no record of how he determined this rela- 

 tion. The skulls are so exactly like those of Dinietrodon and the vertebral 

 column varies so markedly from that of Dinietrodon that the assignment of 

 these skulls to the genus seems at least worthy of reserved judgment. 

 Should the skull of Naosaurus be shown to differ from that oi Dinietrodon, 

 the genus should be placed in a distinct family ; if the skulls are the same 

 the differences are hardly greater than those of very distinct genera.* 



* Discoveries made during the summer of 1906, since this was written, seem to indicate that the skull of 

 Dimetrodon was totally different from that of Naosaurus . See the morphological description of A^aosaurus. 



