HAMILTON": HETKROCEPHALrS, AFRICAX BrRROWlNC. RODENT. 1/5 
6.3 mm.; diastema, 7 mm.; lower jaw, back of angle to front of sym- 
physis, 1 1.6 mm. 
Teeth. 
Tooth Formula. I—, C— , P,-, ]\I,^x2=i6. 
1 o o 
o 
The incisors in both the upper and lower jaw are long and protrud- 
ing, being very sharply pointed. They are modified to play an important 
role in digging. The distance between the two rows of simple round 
molars in the upper jaw is 2 mm. The crowns of the molariform teeth 
of both the upper and lower jaws are figured in Plate II. 
\'ertebral Coll'mx. 
The usual seven cervical vertebrae are present. The atlas, articulat- 
ing with the skull, has a greater transverse than a vertical diameter. It 
measures 8 mm. in width and 5 mm. in height. The neural spine, while 
present, is rudimentary. The neural arch is not greatly curved and 
somewhat weaker than the ventral arch. The transverse processes are 
flattened and short. The transverse foramen is visible. 
The axis is 5 mm. wide and the greatest height, from the odontoid 
process to the tip of the neural spine, is 6 mm. The odontoid process 
is well developed and extends craniad from the inferior arch. The 
neural spine is likewise well developed, constricted somewhat in its mid- 
dle and expanded at its dorsal extremity. It turns slightly caudad. 
The second to fifth cervical vertebrae show no marked variation from 
the usual form. The third has a trace of a neural spine. Unfortunately 
the fourth and fifth neural arches were destroyed when the animal w'as 
speared. 
The eleven thoracic vertebrae measure 24 mm. along the dorsum. 
The slender neural spines are longest in the first six and directed caudad, 
short in the seventh and eighth and lacking in the last three thoracic ver- 
tebrae. The transverse processes are well developed, more so in the 
first than in the last. 
The lumbar vertebrae number seven, with a dorsal length of 21 mm. 
The fourth, fifth and sixth are slightly longer than the others. The 
seventh is the smallest. Spinous processes are small. 
The five sacral vertebrae have a total length of 13 mm. A small 
neural spine is present on the first four. 
Caudal vertebrae number nine. The third, fourth and fifth are the 
