52 REVISION OF THE PELYCOSAURIA. 



as I showed in 1869 [misprint for 1878], the capitular articulation is distinctly to 

 the intercentrum. A second and larger species of that genus, recently come to hand, 

 displays this character to a striking degree, since the intercentrum possesses on each 

 side a short process with a concave articular facet for the head of the ribs. From the 

 slight corresponding contact with the intercentrum seen in the Dimetrodon and other 

 genera, there can be little doubt that this is the true homology of the ribs in the order 

 Therouiorpha. ' ' 



In 1888 (70) the specific name dollovianiis was applied to this species, 

 but witlioTit further description. 



Revised description : 



(i) Spines square at base, rounded above, smooth. 



(2) Third to sixth cervicals with axis through neural arch and middle of cen- 



trum inclined strongly forward. 



(3) Intercentrum of mid-dorsal and lumbar regions small and without termi- 



nal facets for capitulum of rib. 



(4) Lumbars with sharp, low keel on mid line of centrum below, divided by 



longitudinal groove. 



(5) Size, that of D. ii/cisivi/s, 2 to 2.6 meters long. 



The original description of the species was based on the observation 

 that the intercentrnm was large with capitular faces and extended beyond 

 the edges of the centrirni. Cope had not recognized this in the cervical 

 regions of his nncleaned specimens of D. incisivits and others. As soon as 

 this character was made out it became evident that the animal belonged to 

 the genus Dimetrodon. The character of the anterior cervicals, however, 

 demanded that it be retained in a separate species. Other characters are 

 indicated in the morphological description below. 



Dimetrodon macrospondylus Cope. 



Clepsydrops macrosf'ondylus Cope. 



Proc. Am. Phil. Soc, vol. xxii, 1884, p. 35. Also Pal. Bull. 39. 



Type: Twelve presacrals in series, three sacrals, and nine caudals. No. 4012 

 Am. Mus. Nat. Hist., Cope, coll.; from Little Mountain, near Dundee, Archer county, 

 Texas. 



Original description : " The individual by which the species is known, is repre- 

 sented by an axis vertebra, twelve continuous dorsal vertebrae ; nine other continuous 

 vertebrae, of which three are hmibar, two sacral, and four caudal ; also by a part of the 

 ilium, and by the greater part of the dentarj' bone. All of these specimens were 

 found together, and possess an identical mineral appearance. 



"That this reptile belongs to a distinct species from the C. leptoceplialus is readily 

 determined by the form of the dorsal vertebra;. The centra are a little longer than 

 those of that species, but have a smaller vertical diameter. The latter is three-fifths of 

 the former, while in the C. leptocephaliis the two dimensions are reversed, the depth 

 being a little in excess in corresponding parts of the column. The dentary bone, on 

 the contrary, is more robust than that of the C. leptocephaliis., and supports, probably, 

 a small number of teeth. 



