[ 369 ] 



XV. On the Structure of Hooker's Sea-Lion (Arctocephalus hookeri). By Frank 

 E. Beddard, M.A., Prosector to the Society and Lecturer on Biology at Guy's 

 Hospital. 



Eeeeived December 20th, 1887, read December 20th, 1887. 



[Plates LXIV. & LXV.] 



Contents. Page 



I. External Characters 369 



II. Visceral Anatomy 376 



III. Osteology 37S 



I. External Characters. 



THE accompanying drawings (Plate LXIV.) illustrate the three specimens of Hooker's 

 Sea-Lion which were on view a short time since in the Society's Gardens. The drawings 

 exhibit a striking difference in colour between the three individuals. The largest 

 individual (the nearest of the three, as represented) is much darker, and of a greyer 

 colour along the back ; the specimen on the left, which is the one dissected by me, is 

 not so dark in hue, and brown, rather than grey, upon the back ; finally, the smallest 

 individual (that on the right) is the palest of the three. These differences in colour 

 are not sexual, since all three specimens are males ; they are evidently differences 

 due to age. Of the specimen dissected by myself the skin and skeleton have been 

 preserved ; the colour of the ventral parts of the body and of the limbs agrees perfectly 

 with that of the largest specimen figured ; it will not, therefore, be of much use to 

 give a written description of it. 



The external characters of the head of this species are represented more enlarged in 

 the accompanying drawing (woodcut, fig. 1, p. 370). With Hooker's Sea-Lion may be 

 compared Otariajubata and O.pusilla (figs. 2 and 3), of both of which species examples 

 are at present living in the Society's Menagerie. Otaria jubata is at once distinguishable 

 from the other two by the long hairs upon the neck, which form a kind of mane, whence 

 the name Sea-Lion. This appearance, which is very characteristic of the species and 

 apparently confined to that species, is not, by any means, so clearly seen when the animal 

 is wet. 



As compared with those of 0. hookeri and 0. pusilla, the ears of 0. jubata are small 

 in relation to the size of the head ; this difference is considerably more marked in the case 

 of O.jncsilla ; a glance at the drawing (fig. 3, p. 372) at once shows how very much longer 



