OF THE MAMMALIAN 0SS1CULA AUDITUS. 461 



The malleus of a large Orca from Tasmania (PI. LXIII. fig. 7) in general aspect 

 appears like a magnified malleus of Belphinus ; but some of its elements are propor- 

 tionally more highly developed than in the typical genus. The head is large and convex ; 

 the depression on its outer aspect is very deep, and almost recalls Balcena. The size of 

 the processus gracilis and the elements associated with it, connecting the ossicle to the 

 tympanic bone, contrasts strikingly with the reduced proportions of the homologue of that 

 process in the malleus of the Physeteridse. The articular surface is as small as in Belphi- 

 nus, and the facets are of similar type ; but the tubercle from the head of the malleus is 

 far larger than in any of the Dolphins of which the ossicula have been already described. 

 It is much more prominent than in Balcenoptera. At its upper extremity, looking 

 forwards, is a conspicuous rough depressed surface for the insertion of the tensor- 

 tympani tendon. Below is a sharp splinter-like process representing the manubrium. 

 This is much more developed than in Belphinus, or even Globiocephalus ; and instead of 

 being directed backwards, and pressed, as it were, against the head, it is directed con- 

 siderably in a downward direction. The whole tubercle assimilates to its homologue in 

 Balcena, as the same in Megaptera recalls Blatanista in general features. 



The incus of Orca is quite Delphinoid; its short crus is thin and rather long, the 

 stapedial crus very stout. The stapes is similar to that of Belphinus ; it has a minute 

 aperture. 



In a smaller Grampus [Bseudorca meridionalis, Plower) all the ossicula much resemble 

 those of Orca. The malleus has the tubercle bearing the manubrium a little less 

 developed (fig. 6), so as to approach Globiocephalus. 



The homologies of the splinter of bone inflected from the process projecting from the 

 head of the malleus in most Cetacea, and of the rough surface or actual tubercle seen on 

 the point of that process, have been discussed in the description of the ossicula of 

 Balcenoptera ; and specimens in the College Museum illustrate the relations of the soft 

 parts in Dolphins, Whales, and BZyperoodon. I have dissected several ears of Dolphins, 

 Porpoises, and of a Narwhal, and the malleus from the latter dissection (PI. LXIII. 

 fig. 16) is mounted in the special collection of ear-bones on which this treatise is 

 founded. The tendon of the tensor tympani is left attached to the apex of the process 

 from the head ; and the whole membrana tympani is also retained, dried and varnished ; 

 its broad, flat, and pointed process may be seen attached by the point to the splinter-bike 

 manubrium, Hyrtl's "Leiste." All the above preparations conform, on the whole, to 

 the descriptions given by that distinguished anatomist, and by Buchanan, concerning 

 the anatomy of the Cetacean tympanum. The dissection above described was suggested 

 by a figure of the malleus of Monodon in Hyrtl's work. 



The malleus of the Narwhal (Monodon, PI. LXIII. figs. 9 & 16), though essentially 

 the same in type as that of Globiocephalus, is much elongated antero-posteriorly, and the 

 head merges into the broad process in front without any constriction or trace of sepa- 

 ration. The articular surfaces are of equal size (as Hyrtl observes), the upper being not 

 larger than the lower, as in all other Cetacea. The processus gracilis is of the same 

 type -as in Balcena and the rest of the Order ; it is rather long, The incus has an even 



8EC0ND SEEIES. — ZOOLOGY, VOL. I. 3 Q 



