SYSTEMATIC REVISION OF THE SUBORDER. 49 



" The promiuent character which distinguishes this species is the shortness of 

 the ischiatic symphysis. Its extent anterior to the acetabulum is only one-half of the 

 diameter of the latter, while it equals that diameter in the C. gigas. It follows from 

 this, that the crest arising from the anterior border of the acetabulum is abruptly 

 decurved a little anterior to the latter, and descends to the inferior keel at a very steep 

 angle. At its point of decurvature is a prominent tuberosity. The front of the sym- 

 physis pubis presents an obtuse keel, which terminates short of the apex. The 

 inferior border of the acetabulum is not sharply defined, except at its posterior portion." 



Measurements. 



m. m. 



Total length 0.260 Total vertical diameter to superior border of 



Length from posterior border of acetabulum acetabulum o.i35 



forward 148 Length of anterior symphysis 085 



Long diameter of acetabulum 095 



In 1880 (48) Cope published a figure of the vertebral column of Dime- 



trodon incistvus, No. 4008 Am. Mus. The description given was short 



and formed part of the description of the genus quoted above, see p. 43. 



Revised description : 



(i) Spines laterally flattened at bottom, changing to rounded ; finally striate. 



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



centrum nearly vertical. 



(3) Intercentrum small in mid-dorsal and lumbar region, without capitular 



facets at end. 



(4) Lumbars with distinct keel. 



(5) Size medium. From 1.6 to 2 meters. 



The pelvis mentioned (No. 4165 Am. Mus.) as suitable in size to the 

 type skull is only one side and lacks the iliac crest. The peculiar short- 

 ness described is due to the fact that the distal portion of the ischium is 

 also broken away. An evidence of the haste in which the description was 

 written is seen in the fact that "anterior" is used instead of "posterior" in 

 the description of this ischium. 



Dlmetrodon rectlformis Cope. 



Am. Nat., vol. xii, 1878, p. 327. 



Proc. Am. Phil. Soc, vol. xvii, 1878, p. 514. 



Type: Several separate vertebra. No. 1546 Am. Mus. Nat. Hist., Cope, coll.; 

 from Texas. 



Original description : " Its size exceeds considerably that of the Clepsy drops 

 natalis equaling that of the C. ( ? Embolophorus) limbatus Cope. * * * 



" In Dimetrodon rcctiformis, the depth of the centra does not exceed the length. 

 The margins of the articular faces are not twisted, and the articular faces of the zyga- 

 pophyses are horizontal. The opposite is the case in the C. limbatus. The spaces 

 for the intercentra are small ; they are large in C. limbatus. The vertebra described 

 as typical is a posterior dorsal. Here the diapophysis is nearly sessile, and below the 

 line connecting the zygapophyses. Its costal articular surface is narrowed downwards 

 and forwards, almost reaching the recurved border of the anterior face. The neural 

 spine is much elevated, and the sides of the centrum are concave. The inferior 

 articular borders are connected by an acute nearly horizontal edged keel." 



