OF THE MAMMALIAN OSSICULA AUDITUS. 455 



tubercle for the insertion of the stapedius tendon. The crura are very stout, straight, 

 and more divergent than in Balcena. The base was not soldered to the fenestra ovalis 

 in the stapes removed from a skull of an adult male in the College collection, but could 

 be displaced uninjured without any force being required to detach it ; the same was the 

 case with the stapes of an adult Balcenoptera in the British Museum. The base is 

 quite concave towards the vestibule. The aperture between the crura is small and 

 circular. 



The malleus of the small New-Zealand Fin- Whale (Balcenoptera liuttonii, Gray) in the 

 British Museum almost precisely resembles that of B. rostrata ; the tubercle is propor- 

 tionately less developed, and the splint-like manubrium of the northern species is, in 

 B. Imttonii, reduced to a mere rough surface, as in many Dolphins. 



A stapes from the gigantic Steypireythr {Balcenoptera sibbaldii), kindly presented to the 

 College by Professor Turner, has longer crura than that of B. rostrata, but is only half 

 as large again *. 



The malleus of Megaptera novce-zelandice (PL LXII. fig. 32) has its head as flattened 

 as in the last described genus ; but in front, instead of a short round tubercle, is a stout, 

 long, blunt-pointed process curved downwards. On the inner aspect of the latter is a 

 sharp spine (mii), directed backwards, and representing, as in Balcenoptera, the manu- 

 brium. The blunt tip of the process (pm) has a rough surface, evidently for the insertion 

 of the tensor tympani ; and posteriorly, close to the head, is a prominent tubercle, only 

 faintly indicated in Balcena and Balcenoptera, the analogies of which are not evident, 

 though it decidedly is not a muscular process in the last-named genera, as preparations 

 in spirit, already quoted, clearly show. 



I have not had the fortune of examining the incus of a Megaptera, and cannot 

 find a detailed description of it in any work on the Ear or on Cetacea. Van Beneden 

 states that it is small, and that one of its articular surfaces is ill developed (in M. hoops) ; 

 in the illustrations to his work, that ossicle is represented with a body almost as well 

 developed as in Balcena, and the " short crus " is depicted rather stout, long, and pointed, 

 the "long" process not very thick. 



The stapes of Megaptera novce-zelandice, and also that of M. longimana, Gray, has 

 as long crura and as wide an aperture as in Balcena; in a specimen of the former 

 it was found ankylosed to the petrous bone ; in the latter species (judging from an adult 

 specimen in the British Museum) such ankylosis is at least not invariable. 



In the greater length of the process bearing the homologue of the manubrium and the 

 insertion of the tensor tympani, in the form of the stapes and probably of the incus, 

 Megaptera tends more towards Balcena than to Balcenoptera ; but, on the other hand, 

 the flatness of the caput mallei relates it very nearly to the latter ; and the whole process 

 from the head is produced and shaped not so much in the manner seen in Balcena, but 

 rather as in Blatanista. 



The malleus of Neobalcena marginatum (PL LXII. fig. 33) is highly interesting, since, 



* See Appendix to this section. 



t Dr. Hector (Trans. N. Z. Inst. 1872) considers that th is species, known to Dr. Gray under that name through 



3p2 



