SYSTEMATIC REVISION OF THE SUBORDER. 19 



For additional description of the genus by its author see the original 

 description of the skull oi Poliosaurus uniforjnis^ below. 



Revised description of the genus .•* 



(i) No diastema! notch between maxillary and premaxillary. The series of 

 teeth iminternipted. 



(2) No well-defined canine in the maxillary ; several maxillary teeth in the 



anterior third of the series larger than the others. Incisor teeth enlarged. 



(3) Teeth with faint anterior and posterior cutting edges ; not crenate. 



(4) Neural arch of vertebra free from centrum through life. 



(5) Only slight difference in the length of the bottom line of the vertebrce in 



different parts of the column. 



(6) Anterior dorsals without wide face for the intercentrum on the lower edge 



of the anterior face of the centrum ; without sharp and deep median 

 keel. Posterior lumbars not greatly shortened and without a wide 

 extension of the inferior edges of the faces of the centra (compare 

 Elcabrosaiirus baldivini^ p. 28J. 



(7) Spines short. 



(8) Spine of the axis low and broad. 



(9) Limb bones without well-developed articular faces. 



(10) Character not shown. 



(11) Abdominal scutes present. 



(12) Tail probably long. 



(13) A small, probably aquatic animal, not exceeding 700 mm. in length. 



Cope's original description of the genus was based on comparison with 



the genera Dinictrodon and Clepsydrops, but later studies of these forms 



have shown that there is so much difference in different portions of the 



vertebral column that the characters originally used are valueless. The 



first species of the genus described was T. reiroversa, which turns out to 



be the type of Diopens ; on the same page as the description of T. retro- 



versa is the description of T. uniformis^ which is now considered the type 



of the genus under the new name Poliosanriis. The characters listed 



above in the description are those which seem to involve the main lines of 



development in all the genera of the Pelycosauria; as in all the genera 



more detailed desci-iption and discussion will be found in the morphological 



revision. 



Pollosaurus unlformis Cope. 



Proc. Am. Phil. Soc, vol. xvii, 1878, p. 519. Also Pal. Bull. 29. 

 Proc. Am. Phil. Soc, vol. xix, 1880, p. 40. Also Pal. Bull. 32. 



Type: No. 1148 Am. Mus. Nat. Hist., Cope, coll. The anterior portion of a 

 skull; thirteen vertebrce, the first seven, beginning with the atlas, in connected series ; 

 limb bones and the fragments of the atlas ; from Texas. 



Original description : It is described from " vertebne of two individuals with 

 perhaps two others of smaller size. The dorsal centra are characterized by the absence 



*The serial numbers are used for the same characters in all the genera irrespective of the families. 



