342 MANUAL OF ZOOLOGY sect. 



and the phalanges. The carpus or wrist consists of a num- 

 ber of small irregularly shaped bones arranged in two trans- 

 verse rows, proximal and distal, with a central bone between 

 the rows. The metacarpus consists of five narrow bones 

 forming the support of the basal parts of the five digits, 

 and articulating proximally with the distal row of carpals. 

 The rest of the skeleton of the digit is formed of a row 

 of small bones, the phalanges, the last of which — ungual 

 phalanx — is modified in shape to support the horny claw. 



The skeleton of the hind-limb corresponds closely with 

 that of the fore-limb. The pelvic arch consists on each side 

 of three bones which become firmly united together, one 

 of these, the ilium, is dorsal in position, the other two, pubis 

 and ischium, are ventral, the pubis being anterior to the 

 ischium. The ilia articulate firmly with the sacral region 

 of the spinal column ; the pubes unite ventrally in an articu- 

 lation known as the pubic symphysis, and in the lizard the 

 ischia are similarly connected. Laterally where the three 

 bones unite is a cup-like cavity — the acetabulum — which 

 forms the socket for the head of the thigh-bone. 



The thigh has a single long bone, the femur. The leg 

 has two bones, the tibia and fibula, the former, which is 

 internal, being the larger of the two, and the latter in the 

 rabbit not being distinct from the former towards the distal 

 end. In the foot are a number of tarsal bones correspond- 

 ing to the carpals of the hand, a series of metatarsals corre- 

 sponding to the metacarpals and a series of phalanges. 



When the skin of the trunk of the dogfish is removed 

 there will be found immediately beneath it a thick layer 

 of muscle. This is distinctly divided into segments or 

 myomeres similar to those of Amphioxus, and this, with the 

 division of the vertebral column into segments or vertebrae 

 (which, however, do not exactly correspond in arrangement 



