134 PROCEEDINGS OF THE NATIONAL MUSEUM vol.73 



PINNIPEDIA 



Amphibious mammals of fusiform shape and with short tails. 

 The elbow and knee always well within the body contour and with 

 the feet webbed and paddle-shaped. The digits are always five 

 and the fifth toe of the pes is approxmiat^ly equal to the first, both 

 being greater than the three middle toes. The mammae number 

 either two or four. The incisors in living forms are always fewer 

 than 3/3 and the cheek teeth, variable in number, generally consist 

 of four premolars and one molar, but occasionally there are two 

 or three molars {G allotaria) . The molariform teeth never have 

 more than two roots and there is no differentiated carnassial tooth, all 

 these teeth being uniform in character. The milk teeth are small 

 and simple and are shed at an early age. The lachrymal bone is 

 almost always absent; when present it is small and within the orbit. 

 The audital bulla is composite. There is no clavicle. The pre- 

 acetabular length of the innominate is apparently always much 

 less than the postacetabular, at least in living forms. The humerus 

 is massive and the bones of the forearm very broad. The femur is 

 much reduced in length and is flattened. ~There is an os penis. The 

 brain is large and its convolutions complex. The kidneys are lobu- 

 lated and in adults there are large hepatic sinuses of the vena cava,® 

 There are no Cowper's glands. 



External ear small. Both fore and hind feet used extensively 

 during terrestrial locomotion. Area of forefeet great, this extremity 

 being plainly indicated as the more definitely developed for aquatic 

 propulsion, and the axilla is situated at mid forearm. The hind feet 

 assume a plantigrade posture during terrestrial locomotion and the 

 astragalus is without a conspicuous posterior extension, A car- 

 tilaginous extension to each digit occurs and the palms and soles are 

 naked. The nails of the forefeet and those of the first and fifth digits 

 of the hind feet are vestigeal. The testes are scrotal in the adult 

 male. The tooth formula is : 



.9 1 4 1 or 2 



"2 1 "^ 4 1,2, or 3' 



total 34 to 38. The canines are but moderately developed. The mo- 

 lariform teeth have a single main cusp and at times a cingulum, witli 

 occasionally slightly developed anterior and posterior accessory cusps. 

 The skull has a well-developed postorbital process, normally an 

 alisphenoid canal, a mastoid that is usually noninflated, and a mastoid 

 process that is conspicuous and continuous with the paroccipital 



• The presence of these sinuses is merely presumed to be uniform within this order. 



