176 BROOKLYN MUSEUM SCIENCE BULLETIN 3. 5. 
longest, tlie others shortening cephalad and caudad. The total length 
of these vertebrae are ^^ mm. 
Sternum. 
The sternum is CDmposed of the manuhrium, four sternebrae and the 
xiphoid process. The total length is i<j mm. This is considerably longer 
than is found in the larger Hctcrocephalus (jlaber which the Italian work- 
ers studied. The manubrium is 4 mm. wide and without a keel. The 
lack of a keel, a structure associated with burrowing mammals, and par- 
titicularly the Talpidae, is not surprising when we consider the manner 
in which HcterocepJialus digs. It uses its feet very little in digging, the 
head and strong incisors being used primarily for this purpose. Indeed, 
in such a strong digger as the pocket gopher, Geuiiiys, only a trace of 
a keel is found. 
The first sternebra is a third longer than the manubrium and each 
of the others is slightly shorter than the one craniad to it. The xiphoid 
process extends caudad and on its caudal border is the round thin xiphoid 
process. This measures 5 mm. in diameter. 
Ribs. 
Ten pairs of ribs join the sternum, while an eleventh pair is vestigial. 
Parona and Cattaneo record eleven pair of ribs, with a twelfth pair rudi- 
mentary. The ribs are considerably flattened from the lateral to the 
medial surface. Cartilages from the distal end unite the first four ribs 
separately to the sternum. The cartilage portion of the fifth to tenth 
ribs inclusive join together to meet the sternum at a common point. 
A short cartilage strip extends from the atrophied eleventh rib. 
Pectoral Girdle. 
The small scapula is roughly triangular. Its greatest length is 12 mm. 
and its greatest wddth 6 mm. The lateral surface of the scapula is divided 
into two parts by the spine ; the cephalic supraspinous portion is much 
smaller than the caudal infraspinous fossa, occupying approximately one 
third of the lateral surface. The coracoid process is rather long and 
curves cephahuventrad. 
The scapular spine is rather peculiar in this foruL It originates 
slightly craniad from the middle of the vertebral border. It then passes 
cephalo-ventrad for a short distance, then forms a gentle curve with the 
convex side cephalad and terminates slightly below the coracoid process 
in a broadened acromial process. 
