248 THE ANATOMY OF VEETEBEATED ANIMALS. 



conditions intermediate between tliose observed in Notliosau- 

 rus, on the one iiand, and those common in the Lacertilia, on 

 the other. 



The scapula and coracoid give rise by their junction to a 

 glenoidal cavity, into which the thick head of the very short 

 prismatic humerus (Fig. 76, B, H) is received. The distal 

 end of the humerus presents two facets, which articulate 

 with a couple of short flattened polygonal bones, which 

 represent the radius and the ulna [R, V). To these succeed 

 two rows of smaller polygonal ossicles in the place of a 

 carpus : three, representing the radiale, intermeclimn, and 

 ulnare [r. i. u.), lie in the proximal row, and three or four 

 carpalia (Cp.) in the distal low. With the distal carpal 

 bones are connected, by means of the metacarpal ossicles 

 (Mc), longitudinal series of very numerous polygonal bones, 

 adapted together by their edges, and becoming gradually 

 smaller towards the distal extremity of each series. The 

 number of complete series does not exceed five, and may be 

 reduced to three — so that the paddle may be pentadactyle, 

 tetradactyle, or tridactyle. An apparent multiplication of 

 the number of digits arises from two causes : first, the 

 occasional bifurcation of some of the digits ; secondly, the 

 superaddition of marginal bones* to the radial and to the 

 ulnar edges of the manus (m.u., m.r.). There is thus formed 

 a jDaddle, which is unlike either that of a Cetacean, or that 

 of a Plesiosaurus, or that of a Tm-tle — departing more than 

 any of these structures from the ordinary form of verte- 

 brate limb. 



There is no trace of any sternum behind the pectoral 

 arch, but the abdominal walls were strengthened by a num- 

 ber of transverse arcuated bones, similar to those observed in 

 the Plesiosauria, though not so strong. Each is composed of 

 a median piece with pointed ends, and of some three, or more, 

 lateral pieces, overlapping each other's ends, on each side. 

 (Fig. 76, C, V.O.) 



* I leave open the question of a polydactyle manus, such as 

 whether these series of marginal exists iu the Elasmobrauch fishes, 

 -ossicles are remains of the digits 



