INIA GEOFFEENSIS AKD PONTOPOEIA BLAINVILLII. 105 



flattened, and not much expanded in width. The inner surface is quite smooth and 

 slightly concave longitudinally. The outer surface is rougher, and has a rather deep 

 pit a little way below the neck. 



The radius and ulna are considerably shorter than the humerus, contrary to what 

 obtains in most Cetacea. They are very simple, broad and flat bones, but have a con- 

 siderable space between them, owing to the concavity of the contiguous borders of the 

 ulna and radius. The ulna presents the great peculiarity of possessing no rudiment 

 of an olecranon ijrocess. 



Length of humerus 3'2 



Width at middle 1-1 



Width at lower end 1'6 



Length of radius 2-5 



Width at middle 1-2 



Width at lower end 1-4 



, Length of ulna 1'9 



Width at middle 1-0 



Width at lower end 1'6 



The carpal region is large, and composed in the present specimen in great measure 

 of cartilage. There are flve principal ossifications. Intending to discuss fully the 

 homologies of the carpal bones of the Cetacea with those of the terrestrial mammals 

 in my Osteography of the genus Physeter, I will only say here that these appear to 

 represent : — 1 the scapho-trapezium, 2 the lunar, 3 the cuneiform, 4 the unciform, 

 and 5 the magno-trapezoid. They have probably been somewhat disturbed from their 

 natural position by unequal shrinking of the surrounding cartilage in drying. In 

 addition to these five, an oval bone (6) projects from the ulnar border of the carpus, 

 which must represent the pisiform bone, although considerably displaced from its 

 normal situation. The bone which appears to belong to the second row of the carpus 

 near the radial border, and which might well be taken for a trapezium, is probably 

 the first metacarpal, as already determined in other Cetaceans by Cuvier, Gegen- 

 baur, and Van Bambeke. 



The digital portion of the hand consists of five fingers of moderate length, and 

 spreading somewhat from each other. The second digit is the longest, the third nearly 

 approaches it, the fourth and fifth are much shorter. It is possible that the terminal pha- 

 langes of the digits are not present in every case, especially as they do not always ossify 

 before the animal has attained a considerable age ; but the following are the numbers of 

 the phalanges present, exclusive of the metacarpals: — I. 1, II. 5,111. 4, IV. 2, V. 2. 

 The indi\'idual phalanges are thus not numerous ; but they are long in proportion to 

 theii" breadth. 



From the humerus downwards the pectoral limb of Inia presents considerable re- 

 semblance to that of Platanista, both agreeing in the great length of the humerus as 



q2 



