XIII 



PHYLUM CHORDATA 



531 



In the Pinnipedia (Fig. 

 1184) both acromion and 

 coracoid are short, and 

 the scapula is curved back- 

 wards ; there is no clavicle. 

 The bones of the fore-limb 

 are short and stout ; the 

 humerus has a prominent 

 deltoid crest ; there is no 

 foramen above the inner 

 condyle. The ulna is 

 greatly expanded at its 

 proximal, the radius at its 

 distal end. The manus is 

 broad and expanded. The 

 scaphoid and lunar are 

 united to form a scapho- 

 lunar. The ungual pha- 

 langes are nearly straight, 

 slender, and pointed. The 

 ilia are short ; the sym- 

 physis pubis is short and 

 without firm union of the 

 bones. The femur is short, 

 thick, and flattened. The 

 fibula and tibia are com- 

 monly ankylosed proxi- 

 mally. The calcaneum is 

 short and usually without 

 a distinct calcaneal pro- 

 cess ; the lateral digits are 

 usually the longest. 



Skeleton of the 

 Rodentia. Among the 

 Rodents the Jerboas are 

 exceptional in having the 

 cervical vertebrae anky- 

 losed. Generally, as in the 

 Rabbit, the transverse pro- 

 cesses of the lumbar ver- 

 tebrae are elongated. As in 

 the Ungulata, the sacrum 

 usually consists of one 

 broad anterior vert :bra 

 followed by several 

 narrower ones. The caudal 

 region varies in length in 



