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



transmission of an artery unsupported by any bony canal, but may be considered as 

 well (for reasons given above at lengtb) to indicate an approach to the Primates. 



VI. Judging from their ossicles it may be said that the Ohiroptera are very closely 

 allied to the Insectivora far more than to any other order of mammals. 



The Ossictjla of the Cetacea. 



The highly specialized tympanic and petrous bones of the Whales and Dolphins are 

 now familiar, not only to the anatomist, who confines his studies to recent animals, but 

 also to the student of palaeontology, on account of their great density and consequent 

 durability. The already known peculiarities of the soft parts in the auditory apparatus, 

 as they exist in this Order, may be conveniently studied in the fine preparations made by 

 Hunter, and now preserved in the Museum of the Royal College of Surgeons *. His 

 observations, quoted in the Catalogue t, are full and satisfactory as far as concerns the 

 common species described therein, but preparations of the tympanum and labyrinth of 

 rarer types remain unrepresented in that series. Further researches in the anatomy of 

 the cetacean tympanum and membranous labyrinth are much to be desired. 



But, in accordance with the scope of this paper, the morphological characters of the 

 ossicula must alone occupy our attention. I will describe them relatively, as touching 

 the distinction of each ossicle in the different genera, and comparatively as regards the 

 homologies of the several parts of the highly modified cetacean ear-bones to correspond- 

 ing portions in the more familiar types of terrestrial or partially terrestrial mammalia. 



In the College collection there is one fine specimen of the malleus of Balcena mys- 

 iicetm (PI. LXII. fig. 28), and another, precisely similar in character, attached to the 

 tympanic bone (No. 2438, Osteol. Ser., PI. LXIII. fig. 13), probably from B. australis. At 

 the first glance, no part of this bone, as it is seen in other animals, can be distinguished 

 in these specimens, excepting the articular surface ; after a little observation, the pro- 

 cessus gracilis will be recognized ; and by further careful study of the specimen, the 

 observer will find that the modifications are not quite so great as they at first appear. 



The peculiarities of this ossicle may be rendered more intelligible by first examining 

 it in situ, as in PI. LXIII. fig. 13, which includes part of the (left) tympanic and petrous 

 bones in B. australis and is viewed from in front. The malleus is seen to be firmly 

 ankylosed to the tympanic (tb) by its processus gracilis (pg) and by certain appendages 

 (l.,phm), presently to be explained. That ossicle is, in Balcena, anterior to the membrana 

 tympani ; and the processus gracilis runs, not forwards, but outwards, to a special pro- 

 jection of the margin of the tympanic bone to which it is attached. This projection 

 probably represents the anterior extremity of the annulus tympanicus of other mammals, 

 the part in front being an extension of that ossification to surround the beginning of the 

 Eustachian canal. The petrous bone {pel) lies much above the tympanic; hence the 

 unusual position of the articular surface of the malleus, as Cuvier has observed. It 

 follows that the homologous parts of the malleus of. Balcena and the same bone in an 

 ordinary mammal will not be found in the same respective aspects of each bone. 



* Nos. 1582-1598 b, Physiological Series. f Physiology, vol. iii. p. 115. 



