14 MAMMALIA. 



lies anteriorly is very slightly moveable. In the Mole it gives 

 off superiorly and anteriorly a free hook-shaped process. In the 

 Edentata in particular, the ulna is very long, and its large olecranon 

 often provided with hook-shaped processes. In the Seals both bones 

 of the fore-arm, as well as the humerus, are bent in a peculiar man- 

 ner in the form of an S. In those herbivorous quadrupeds which 

 are organized for rapid motion, both bones lie behind each other, 

 are immoveably united, and more or less anchylosed. The latter is 

 the case in some Pachydermata, such as Dycotyles and Hippopota- 

 mus, but not in the Elephant. In the Horse the ulna has an olecra- 

 non of considerable size, but which soon becomes thinner and blends 

 with the very upper portion of the radius, far from its inferior ex- 

 tremity, so that the latter bone is the main support of the leg. The 

 construction is similar in the Cheiroptera, where the perfectly rudi- 

 mentary, short and spine-shaped ulna frequently has appended to it a 

 discoid olecranon, comparable to a patella, as in Pteropus, Nycteris, 

 Rhinolophus,' &c. 



The Carpus always consists of several small variously shaped 

 bones ranged in a double row, the number of which varies between 

 5 and 11 ; very frequently there are 8, as in Man, or 7, 9, or 10, as 

 in the Apes. The first or posterior row exhibits in the Rodentia, 

 Carnivora, and Marsupiata a tendency to a reduction of the num- 

 ber (4), by the first two bones uniting so as to form a scapho- 

 lunar bone, as in the Hedgehog, while the anterior row is increased 

 to 5, by the interposition of an additional ossicle between the 

 scaphoid, os magnum, and cuneiform bones. The pisiform bone 

 is frequently of considerable size, and serves as a point of attach- 

 ment to a flexor muscle of the hand. The Whales have only from 

 3 to 5 dice-shaped carpal bones lying between thick tendons and 

 masses of ligament. In the very broad hand of the Mole, there is 

 superadded to its internal border an 1 1th very large and sickle-shaped 

 bone. 



The Metacarpus consists for the most part of five elongated 

 bones, which dwindle down to four and three in the Rhinoceros, 

 and in the Ruminantia and the Horse to a single bone, though in 

 the latter animal there are two shorter styloid appendages, which 

 are the rudiments of two of the lateral metacarpal bones. Five 

 fingers are usually met with, whereof the thumb is frequently rudi- 

 mentary, and consists only of a single small bone, which is also 

 occasionally wanting. The Ruminantia have generally two fingers ; 

 the hinder claws, however, and their small phalangeal bones. 



