SYSTEMATIC REVISION OF THE SUBORDER. 



47 



Dlmetrodon giffanhomogenes sp. nov. 



Type : Two cervicals, eleven dorsals, six lunibars, five caudals, perfect right half 



of pelvis. No. 112 University of Chicago ; from Coffee creek, Baylor county, Texas. 



Description : This species is very near Dimetrodon gigas in size and character 



of the vertebrse and pelvis. It differs from the other species in the shape of the 



spines, the character of the keels on the cervical vertebrae, and the shape of the pelvis. 



(i) Spines broad transversely at base ; becoming oo-shaped above. A tendency 



for the ends to be tuberculate. 



(2) The third to the sixth cervical with axis through spine and middle of 



centrum vertical. 



(3) Interceutrum small in mid-dorsal and lumbar regions, without terminal 



facet for capitulum of ribs. 



(4) Character not shown. 



(5) Size nearly as great as Dimetrodon gigas^ 2.6 meters at least. 



O o 



S60mm gj(,^ 



CO o o 



f30mm 600 mm 



CO cz) a 



230 mm 630 mm 850 mm 



too mm 



Fig. 14. — Cross-section through the spines ot various species ot Dimelrodon, al approximately the same 

 level above the neural arch. The figures give the distance above the base. a. D. macrospondylus. 

 No. 1019 University of Chicago. A lumbar, b. D. gigas. No. 1002 University ot Chicago. 

 The ninth dorsal, c. D. incisivus. No. 1001 University of Chicago. The fourteenth vertebra. 

 d. D . giganhomogenes, No. 1 1 2 University of Chicago. An anterior dorsal. 



Dimetrodon IncisiTUS Cope. 



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



Proc. Am. Phil. Soc, vol. xvii, 1878, p. 512, plate vi. 



Type : An imperfect skull, consisting of maxillaries, premaxillaries, and frag- 

 ments of the preorbital portion of the skull. No. 41 16 Am. Mus. Nat. Hist., Cope, 

 coll.; from Texas. 



Cotype : A vertebral column complete from axis to first caudal and a fragment 

 of the muzzle. Premaxillar>' and part of maxillar>- in position. No. 4008 Am. Mus. 

 Nat. Hist., Cope, coll.; from Little Wichita river. Archer county, Texas. 



