402 MR. A. H. G. DORAN ON THE MORPHOLOGY 



without a trace of an aperture between them in any specimen I have seen, and a narrow, 

 rather thin base, concave horizontally. The whole is shaped like a bottle with a short 

 neck, and very unsymmetrical on account of the outline of the anterior crus being by 

 far the most convex. This stapes strongly resembles that of Macrorhinus, while Otaria 

 closely assumes in its stapes the type of the Dolphin. These two animals approach, 

 though less nearly, the Sirenian form of that bone. 



The Cystophorina, the first subfamily of the Phocid^i, are remarkable for the great 

 difference between the auditory ossicles of two well-known species otherwise closely 

 allied, and often included in the same genus, viz. the Hooded Seal ( Gystophora cristata) 

 and the Elephant Seal (Macrorhinus proboscideus). The latter most resembling Tri- 

 chechus in its ear-bones, it will be described first. 



The head of the malleus of Macrorhinus proboscideus (PL LIX. figs. 23, 24) is flat- 

 tened laterally, as in the Walrus ; it is still larger in proportion to the rest of the bone, 

 but is rather triangular than lozenge-shaped, the upper aspect being rounded off and 

 very broad, not produced to a blunt point. Anteriorly the head is marked by a deeply 

 concave pit, quite triangular, its basal boundary being uppermost — that is, corresponding 

 to the broadest or upper part of the whole head. The articular surface is very small, 

 not extending to the periphery or upper part of the broad posterior aspect of the malleus. 

 It exhibits the extreme of vertical narrowness and horizontal breadth so general among 

 the Phocidse. Both facets have a very prominent vertical convex ridge ; so that the 

 whole surface is horizontally quite convex, though laterally slightly but distinctly con- 

 cave ; the groove dividing them is extremely faint. The neck is very short ; and the 

 processus gracilis springs from it as a prominent splinter of bone, connected with the 

 head by a thin and very brittle layer of compact, not lamellar bone. There is no trace 

 of a muscular process. The manubrium is very short, though not quite as short as in 

 Trichechus and Stenorhynchus ; it forms almost a perfect right angle with the neck ; the 

 base is very broad ; it is much recurved at the tip, which is spatulate ; the outer aspect 

 is very wide at the base, corresponding to the processus brevis ; it widens again near the 

 termination. 



In general configuration the malleus of M. proboscideus closely resembles that of 

 Stenorhynchus ; indeed the only differences I can find are in the wider articular surface 

 and the still shorter manubrium, forming a wide obtuse angle with the neck in the latter 

 Seal. In Trichechus the articular surface is different from that of Macrorhinus, and the 

 manubrium, is still shorter. In Gystophora and Phoca the neck is long, and the manu- 

 brium forms a very wide angle with the rest of the bone. 



The incus is of unique form. It is more than double the bulk of its own malleus, and 

 exceeds in size its representative in Balcena and in most specimens of Manatus. The 

 great feature is the immense development of the posterior part of the body, which leans 

 over to the outer side of the crura to an extraordinary degree. The anterior part 

 projects forwards like a lip, and is also inclined somewhat outwards at its uppermost 

 part. The articular aspect is very small, occupying, to an equal extent, both the pro- 

 jecting posterior and the more level anterior part of the body ; internal to it is a deep 

 pit, divided by a groove, which runs in a line with the ridge dividing the facets. This 



