Width across occipital plate 52 



Length, bottom line of — ^ , ' 



Axis 21 15th! 



3d cervical 22 i6th, 



4th " 22 i^th! 



5th ■' 21 isth, 



MORPHOLOGICAL REVISION OF THE SUBORDER. 1 37 



Mtasurements. — No. 4062 American Museum. 



mm. mm. 

 Diameter occipital condyle : Length, bottom line of — 



Horizontal 15 6th cervical 16.5 



Vertical 11 nth, a dorsal 19 



I2th, " 20 



16.S 



20 



20 



20 



21 



20 



Height of centrum posterior to neural arch .... 17.5 23d, a lumbar 17 



No. 2152 American Museum. 



mm. mm. 



Length of humerus 147 Width, distal end 57 



No. 1060 University of Chicago. 



mm. mm. 



Anterior face of centrum : Posterior face of centrum : 



Vertical diameter 12 Vertical diameter 11 



Horizontal diameter 10 Horizontal diameter 12 



Length, bottom line of centrum, 17 mm. 



Otlier specimens of this species are Nos. 1015 and 1017 Am. Miis., and 

 180 University of Chicago. 



Dimetrodon navajovicus Case (p. 56, plate 27). 



Characteristic specimens: No. 2299 Am. Miis. : The t>-pe. No. 2288 Am. Mus. 

 Nat. Hist, Cope, coll. ; from New Mexico. No. 2285 Am. Mus. Nat. Hist., Cope, coll. : 

 Collective number covering many lots, but mostly this species ; from New Mexico. 

 No. 1034 University of Chicago. No. 1046 University of Chicago. 



There is no fragment of the skull preserved. 



The Iiutnerus, described from No. 2285, is most easily recognizable in this species; 

 it is of the general form of Dimetrodon incisiviis with well-developed articular surfaces, 

 but the proportions are notably different. The head is broad, with the usual oblique 

 face, but the face does not extend to the radial border as in Dimetrodon incisivus. 

 The radial crest joins the proximal portion of the bone at an obtuse angle, and the 

 line of union is marked on the posterior side by a sharp ridge. The crest is very short, 

 beginning low down on the distal end and looking rather like a wide process than a 

 ridge; it tenninates in a broadened apex with a smooth surface for ligamentous attach- 

 ment. The upper end is separated from the articular face by a wide concave interval. 

 The shaft is more slender compared to the ends than in other species. The lower 

 end has well-developed radial and ulnar faces. The entepicondyle is very long, 

 extending so far inward that a line drawn straight down from the entepicondylar fora- 

 men would divide the distal end of the bone into two nearly equal halves. In other 

 species there is not more than a third or fourth of the distal end inside of such a line. 



No. 2299: The femur has a wide proximal end, with a deep depression on the 

 posterior face, with a prominent process on the inner side. The lower end has stout 

 and well-developed condyles separated on the posterior side by a deep groove, but the 

 articular faces lie so much on the posterior face that they are not separated by the 

 distal notch. 



