NATURAL SCIENCES OF PHILADELPHIA. 25 



Tlie atlas is characterized by the nearly equal width of the portion of the 

 neural canal above and below the constriction, the narrowness of the wing 

 outside the articulating surfaces, and the elongation of the latter. The infe- 

 rior apophysial articular surface is broad, rounded, and separated by a high 

 ridge from the anterior face of the inferior limb. The inferior lateral pro- 

 cess is opposite the middle of the articulating surface ; it is short, obtuse ; the 

 superior is small, acute. 

 Width of canal above constriction 2 2-6 



" " below " 2 2-6 



" wing from posterior articular surface 6 



Vertical diameter of posterior articular surface 2 3 



The body of the axis is short, and the lateral alas longer and thinner than in 

 the a ng u s t ata, though not extending so far beyound the articular facets. 

 The inferior articular surface is longer than broad and occupies two-thirds the 

 surface of the body. The neural spine is short, flat, and terminates obtusely, 

 over the penultimate cervical. The zygapophysial articulation marks three- 

 fifths the distance between the external alar angle and the tip of the neural 

 spine. 



In. Lin. 



Total transverse diameter 6 10-2 



" of centrum 2 4. 



Heighth of neural canal 1 8-2 



Length of neural spine 2 1-2- 



Of the remaining cervical vertebrie, the third is distinct, and has very short 

 lateral processes, the superior longer, originating with the neurapophysis from 

 a very broad base. Its neural arch is completed above bya loose suture. The 

 superior lateral process diminishes and is reduced to notliing on the filth, ap- 

 pears higher up on the sixth, and commencing at the zygapophysis on the 

 seventh is very elongate and much recurved, its extremity being opposite the 

 articulation of the fourth or fifth. The inferior lateral process increases to the 

 fifth, where they are nearly cylindrical, three-quarters inch long by a half broad, 

 and directed downwards at an angle of 45°, These processes rapidly diminish 

 and are reduced to nothing on the seventh vertebra. 



Dimensions of seventh cervical vertebra : 



In. Lin. 



Length of body 7-4 



Transverse diameter of same 2 62 



" " of neural canal 2 7 8 



" extent of diapophysis from canal I 10-8 



Height of neural canal 1 7-4 



The dorsal, as well as the other vertebrae, are distinguishable from those of 

 the other species by their great breadth as compared with their length. The 

 costal articular surfaces of the centra are not distinct. 



Dimensions of the third dorsal : 



In. 



Length of body 1| 



Anterior vertical diameter 1 4-8 



Anterior height of canal 2 1-8 



Breadth canal at diapophysis 2 6-8 



In. 



Span of neural arch 3^ 



Width " " 



Heighth neural spine (from be- 

 hind). 



The lumbar vertebrae possess longer diapophyses than those of the an g u s- 

 t a t a and c o n c r e t a, which are also less dilated distally on the anterior 

 margin. That of the first is nearly truncate. 



Hs dimensions are : 



In. 



Length body 2 3-16 



Anterior transverse diameter. 2^ 



Height canal (anteriorly) 1 15-16 



Width at diapophyses 1| 



Epiphysis to anler. extremity 



of diapophysis 2 15-16 



1869.] 



In. 

 Same to posterior extremity.. 3j 

 Floor of canal to zygapopl\y- 



sis 2 1-16 



Zygap. to apex of neural 



spine 2 7-16 



