I40 REVISION OF THE PELYCOSAURIA. 



of the spine is not closed at the apex. On several of the vertebra the lowest transverse 

 process is double, but the sides of the same vertebrae differ from each other in this 

 respect in some instances. 



"The two sacral vertebrce are not coossified, and the zygapophyses are well 

 developed and distinct, as are the intercentra. The latter are flat, and but little 

 developed in the upward direction. The neural spines are rather elevated and slender. 

 They are compressed without cross-processes, and the apex of the spine has small 

 tubercles. 



^'•Ribs : The ribs are long and well curved, and are moderately compressed on 

 their proximal half, and cylindric for their distal. The head is well distinguished 

 from the tubercle, as in the manner of a mammal. That is, the tubercular surface is 

 sessile on the convexity of the rib, and pedunculate. In this respect these ribs differ 

 from the usual form of two-headed reptilian ribs. The head is so long on the anterior 

 dorsal vertebrae, as to articulate with the posterior edge of the vertebra in front of 

 the one with which its tubercle articulates. It becomes shorter on the posterior part 

 of the column, articulating with the edge of the rib which supports the tubercle. On 

 the caudal series the head is retracted so as to be close to the tubercular articulation, 

 which is the most extensive, and which is deeply notched on one of its faces. Tliis 

 gives the appearance of a three-headed rib in this genus and in Dimetrodon. * * * 



Measurements. 



No. I. (Skull.) "'• No. 3. (Vertebra.) 



Depth of muzzle at sixth tooth from last 0.172 Diameters centrum dorsal vertebra : m. 



Length of skull posterior to same tooth 232 Antero-posterior o-039 



Diameters of orbit : Transverse 034 



Antero-posterior 057 Vertical 035 



Vertical °56 Expanse prezygapophyses do 041 



Vertical depth from line of eyebrow to end of Diapophyses do 082 



quadrate 200 Elevation of neural spine to first process 024 



Width of condyles of quadrate 050 jransverse diameter of process 025 



Diameters of crown of sixth tooth : Diameters of neural spine at process ; 



Vertical 028 



Antero-posterior 03° 



Antero-posterior 014 Transverse 028 



Transverse...... •■ ';":"Z'l""X. °^^^ Length of the two sacral vertebra? 084 



Thickness of max.llary bone at s.xth tooth.. 022 J^^.^^ ^^_ 



No. 2. (Vertebra probably of No. i.) ^^^^^^ ^^^^^ ^^ ^^ „^„ 



Diameters of dorsal neural arch, with zygapo- .^^^ ^^ ^^ ^g_^ 



P'T^'' . ■ 06^ Length of^ 



Antero-posterior 064 ^g„ 



Transverse (posterior) .036 h d f 'h 045 



Diameters of neural spine near base : Head ot n ■■■■'■■■■■■■" " 



. ^ ■ ^ „,, Transverse diameter of rib just beyond tubercle .017 



Antero-posterior 033 ^'i" . . j n-.r. 



Transverse 027 Antero-posterior do 0-0 



In 1892 Cope gave a further description of the temporal region of the skull 

 accompanied bv a restoration. "The orbit is in the posterior part of the skull, and 

 the muzzle is greatly elevated and compressed. The zygomatic (quadrato-jugal) is 

 greatly decurved posteriorly, and the supratemporal is accordingly decurved also. 

 The postfrontal is a narrow bone, wider than long, and it has connection with the 

 frontal, parietal and postorbital only. The postorbital is an L-shaped structure, of 

 which the shorter limb is inferior, extending to the jugal, while the longer limb is 

 posterior, extending to the supratemporal, in contact with the parietal. It encloses 

 no foramen with the latter; but it encloses a larger foramen with the jugal, zygomatic 

 and supratemporal at the other boundaries. This is the infratemporal foramen of 



