128 REVISION OF THE PELYCOSAURIA. 



Specimen No. looi University of Chicago presents one difference from No. 

 4008 Am. Mus. that might be regarded as of specific vaUie. In No. 4008 the spine 

 of the third cervical curves forward and lies close against the posterior edge of the axis 

 much as it does in Dimetrodon dollovianus, but in No. lOOi University of Chicago the 

 spine rises vertically from the centrum ; the base is wide antero-posteriorly, the front 

 edge very thin, and the posterior edge wider and grooved ; the sides are marked by 

 coarse striations. The spine contracts near the middle through a rugose swelling to 

 a smooth cylindrical shaft, which curves forward over the axis. The distal end of the 

 spine is marked by a distinct pit for ligamentous attachment (plate 15, fig. 2 and 

 text-fig. 37j. The axis differs from that of No. i University of Chicago by having 

 the posterior edge of the spine not so broad and without the great cavity just above 

 the posterior zygapophysis. The bottom line has no well-defined keel, and the lower 

 edge of the posterior face is much lower than the edge of the anterior face. 



These differences are so slight as to be possibly individual, or varietal, characters, 

 and are accepted as such until further evidence proves their specific value. 



Measurements. — No. i University of Chicago. 



mm. """• 



Total length of humerus 181 Greatest breadth: 



° ,, Proximal end 4^ 



Greatest breadth : Distal end 38 



Distalend.. "7 joj^i length of femur 220 



Proximal end 9o breadth of proximal end 73 



Diameter of shaft at center 24 distal end across condyles 69 



Projection of deltoid ridge 35 Greatest diameter of shaft at center 36 



Total length of ulna 202 loxaS. length of tibia '77 



Greatest breadth : Breadth, upper end from side to side 72 



Distalend 37 Before back 5' 



Proximal end 55 Greatest diameter of shaft at center 21 



Total length of radius 146 Greatest breadth at distal end 44 



No. looi University of Chicago. 



tn^n. 



mm. 



Height of spine of the 14th vertebra from center Vertical height of spine of 3d cervical above 



° ^ _ g center of neural canal I44 



of neural canal /4 Antero-posterior diameter of spine at base 27 



Length, bottom line of centrum 29 xhickness of spine at middle of base 6 



Antero-posterior diameter of spine at base 5 Length, bottom line of centrum 25 



No. 4008 American Museum. 



mm. """■ 



Length, bottom line of 12th, a dorsal 22 Width of keel on bottom bne . 13 



L,engui, uui „„„^,i ,rrh lo W dth of centrum at notochordal canal 12 



Height of centrum posterior to neural arch .... 30 ^^.^^^^ ^j ^^^^^j^^ j^^^ ^j centrum at level of 



Vertical diameter of anterior and posterior faces. 34 notochordal canal 25 



Width of keel on bottom line i Length, bottom line of last lumbar 15 



Width of centrum at notochordal canal 10 Total length of centrum 28 



Width of anterior face of centrum at level of Height of centrum posterior to neural arch .... 29 



notochordal canal 24 Vertical diameter of anterior and posterior faces. 35 



Length bottom line of i8th, the first lumbar. . . 21 No keel present. 



Total length of centrum 28 Width of centrum at notochordal canal ...... . 24 



Height of centrum posterior to neural arch 25 Width of anterior ace of centrum at level of 



Vertical diameter of anterior and posterior faces . 30 notochordal canal 31 



Dimetrodon dollovianus Cope (p. 51; plates 23 and 24). 



Emboto^horus dolloviatius. 



Characteristic speciviens: No. 4064 Am. Mus.: The type. No. 114 University 

 of Chicago: A very complete specimen, including a skull lacking only the posterior 

 temporal region ; the lower jaws ; thirty-five vertebrae, beginning with the atlas, from 

 the seventh presacral to the second caudal connected ; the shoulder girdle ; the fore 

 limb and incomplete fore foot; the pelvis. From Coffee Creek, Vernon county, 



