No. 2.] AMPHIUMA MEANS. 38 1 



lation of the two bones of the forearm. These bones are 

 approximately of the same length, but the radius is the stronger. 

 The carpals are not ossified. They are five in number. The 

 ulna articulates with the ulnare only, but the radius articulates 

 with both the ulnare and radiale. There may be either two or 

 three metacarpals. Formerly this difference in number served 

 as basis for the specie classification, didactyla and tridactyla. 

 Professor Ryder has since demonstrated the identity of the two 

 forms. The second and third digits have two phalanges each. 

 The fourth digit has only one. 



The hind limb of Ajiiphiiima is fully one-third longer than 

 the fore one. The femur has a well developed, cartilaginous 

 head and a prominent trochanter. It broadens gradually from 

 the middle to the distal end. The tibia and fibula are a trifle 

 over one-half the length of the femur, and are approximately 

 equal to each other in strength. The tibia is largest at its 

 proximal end, but the two ends of the fibula have equal surfaces. 

 These bones articulate with the tibiale and fibulare of the 

 tarsals. The third tarsal supports the third and fourth meta- 

 tarsals, and the tibiale supports the second metatarsal. The 

 second and third metatarsals have each two phalanges, but the 

 fourth has only one. All the phalanges and metatarsals are 

 well ossified, but the tarsals are cartilaginous. The girdle 

 bones are less perfectly formed than the limb bones. The 

 shoulder girdle consists of a cartilaginous coracoid, a bony 

 scapula, and a cartilaginous suprascapula. There is no evi- 

 dence of true sternal elements. The pelvic girdle is more 

 complete, having an ischium, ilium, and pubes. The ischium 

 and pubes are united to each other and also to their fellows of 

 the opposite sides, so as to form a shield-like plate, which is 

 composed of cartilage, with the exception of two discoid ossifi- 

 cations in the posterior parts. The acetabulum is entirely 

 cartilaginous. The ilium proper is well ossified, very slender, 

 and surmounted by a cartilaginous style which is attached to 

 the sacral rib of the sixty-third vertebrae on the right side and 

 the sixty-fourth on the left. I think Mr. F. A. Lucas of 

 Washington was the first one to observe this asymmetrical 

 disposition of the iliac bones. 



