156 



Ml!. "\V. IT. FLOWEB OX THE SKELETON 



The stylo-liyals have the usual form, aud are -±"-5 long, and 0"'6 in greatest diameter. 



The spinal column, which is quite complete, consists of fifty-one vertebrae, seven 

 belonging to the cervical, twelve to the dorsal, ten to the lumbar, and twenty-two to 

 the caudal region. The respective lengths of these four regions in the articulated 

 skeleton are 3 inches, 17^ inches, 16^ inches, and 30 inches. 



In the cervical region, the atlas and axis are united, and the remaining vertebra are 

 free, as appears to be the rule in the genus Belphinus. The component parts of the 

 conjoined mass formed of the first two vertebrae can be readily defined. The bodies are 

 thoroughly confluent, though a superficial groove marks the limit of each with tolerable 

 certainty. The arches in their first part, or pedicle, are distinct, and have between them 

 a considerable oval aperture for the transmission of the second spinal nerve. Above 

 this, opposite the zygapophysis, they are firmly united ; the laminae are then separated 

 on either side for a space of half an inch by a linear fissure ; and, finally, the spines are 

 completely confluent. This conjoined spinous process is high, massive, sloping back- 

 wards, strongly ridged on its median upper or anterior border, and with a rounded and 

 somewhat depressed and truncated apex. The pedicle of the arch of the atlas is very 

 much thicker than that of the axis, and on its anterior border has a deep notch, almost 

 converted into a foramen on the left side, for the passage of the first (the suboccipital) 

 spinal nerve. Both atlas and axis have a single transverse process on each side, that of 

 the former long, stout, rugged, rounded at the end, and directed slightly downwards 

 and backwards. The transverse process of the axis is a small, rough, and rather com- 

 pressed tubercle, placed nearly on a level with the root of the last, and directed some- 

 what upwards as well as backwards. The dimensions of these vertebrae are : — 



4-0 

 5-7 

 3-6 

 1-8 

 1-6 

 1-5 

 1-5 

 1-7 

 1-5 



4-0 

 2-1 



The remaining cervical vertebrae have greatly compressed subcircular bodies. The 

 under surface of each has a fringe of rough exostoses growing on each side of the 

 middle line, and leaving (as seen in the figures, PL XVIII.) a deep notch at this part. 



Breadth of articular surfaces on atlas for condyles 

 Breadth between tips of transverse processes of atlas 

 Breadth between tips of transverse processes of axis 

 Greatest breadth of spinal canal, inside arch of atlas 

 Greatest breadth of spinal canal, inside arch of axis 



Height of spinal canal, inside atlas 



Height of spinal canal, inside axis 



Breadth of body of axis at posterior end . . . 



Height of body of axis at posterior end .... 



Height from lower surface of body of axis to apex of spinous 



process 



Length of upper or anterior edge of conjoined spinous process 



