OF THE MAMMALIAN OSSICULA AUDITUS. 405 



merely indented) by a faint groove. The neck is thin and suhcylindrical, rather long, 

 but never so regularly cylindrical or so prolonged in this species and genus as in Cysto- 

 phora cristata. Close to and a little below the articular surface there springs from the 

 neck a little projection in the form of a much-truncated cone, directed inwards and 

 slightly downwards and forwards ; its extremity is quite plane and round, and articulates 

 with a similar projection from the incus (PL LIX. fig. 28, & LX. fig. 1, eas). This 

 peculiarity, as well as the concavity in the head, is already well known to anatomists. 

 The processus muscularis is absent. The manubrium closely resembles that of Cysto- 

 pliora, but is slightly longer ; besides, it has a distinct processus brevis, which is curved 

 upwards towards the neck in well-preserved specimens. 



The incus closely resembles that of Cystophora ; the articular surface is surrounded 

 posteriorly and internally by a deep ear-shaped depression ; the posterior crus is very 

 short, and generally thick; the stapedial crus is short, rather thin, boldly curved 

 inwards, and deeply grooved on its internal aspect, bearing on the outer and interior 

 aspect of its base a projection as well developed and similar in form to that on the back 

 of the neck of the malleus, with which it articulates (PL LIX. fig. 28). When these 

 ossicles are articulated, a small foramen exists between the ordinary and the peculiar 

 phocine articulations (PL LX. fig. 1). The extremity of the processus longus, which is 

 rather thin, bears a Sylvian apophysis, happily compared in its form by Hyrtl to a house- 

 fly's proboscis. 



The stapes has very stout, rather short and crooked crura ; the anterior is most bent ; 

 they diverge considerably towards the base, and have an almost circular aperture between 

 them ; the base is also thick, and quite concave in its long diameter. 



Such are the ear-bones of JPhoca vitulina ; and no essential variations have been found 

 in numerous specimens examined by me at the Royal College of Surgeons. In a 

 specimen of the left ossicula of the Harp-seal (Phoca grcenlandica) (PL LIX. fig. 30) 

 the neck of the malleus does not bear a trace of the singular extra articular process ; 

 but Hyrtl has observed such a projection in this species. There is a faint protuberance 

 at the back of the neck, close to the manubrium, which may resemble the processtis 

 muscularis seen in P. barbata. The neck is nearly as long (though not nearly so regu- 

 larly cylindrical), and the manubrium as short, as in Cystophora. The incus (PL LX. 

 fig. 3) wants the extra articular projection, as might be expected ; its crura are otherwise 

 exactly similar to P. vitulina ; the limbs of the stapes, though rather straighter, are quite 

 as divergent. 



In the Bearded Seal (P. barbata, PL LIX. fig. 29) the extra articular process of the 

 malleus is quite absent ; but on the back of the neck, near the root of the manubrium, is 

 a distinct processus muscularis (absent in the left malleus of one specimen in the College 

 collection, though present on the right side). In describing the Stenorhynchina, I dis- 

 cussed the relationship of the true processus muscularis to the extra articulating process 

 and the deep depression found on its site in that Seal. The fact that in P. barbata there 

 is a true processus muscularis much lower down the neck than the articulating process 

 is placed in P. vitulina, is against the probability that the latter is a modification of the 

 former ; but the insertion of the tendon of the tensor tympani into a deep pit situated in 



SECOND SERIES. — ZOOLOGY, VOL. I. 3 I 



