452 MR. A. H. G. DORA.N ON THE MORPHOLOGY 



tubercle can hardly be fairly denied to be the homologue of the processus inuscularis. 

 Taking these assertions for granted, and recognizing henceforth in this treatise the 

 curved process as the handle of the malleus, it will be shown that the manubrium is far 

 better developed in Balcena than in the Dolphins or Sperm-whales, and still more than 

 in the Ziphioid Physeterida?. 



Prom the malleus to the tympanic bone runs, almost directly outwards, a process over 

 half an inch in length. It is made up of two stout splints or columns, one forming its 

 posterior, the other its anterior border, and a broad flooring of thin bone connects 

 them by their inferior borders ; this latter is continuous with the floor of the excavation 

 in the head of the malleus, the posterior raised and everted margin of that cavity 

 running to join the posterior splint, the anterior coming distinctly from the corresponding 

 margin of the depression in the malleus of B. australis ; in that of B. mysticetus the 

 anterior splint is given off in front of the groove, at least so I find it in the spe- 

 cimens I have examined ; but this appears to be a trifling point, probably subject to 

 variety. 



The whole of this process, highly characteristic of the Cetacea, has for years been 

 recognized by most authorities as the processus gracilis. One anatomist, Buchanan, who 

 has carefully studied the anatomy of the ear in this Order, and written a most lucid 

 description of the Whale's membrana tympani, represents this bony connecting medium 

 in a Plate *, and there calls it " the long handle of the malleus ;" whilst the process mn 

 in PI. LXII. fig. 28, & PI. LXIII. fig. 13, at the end of this paper, 'is represented in 

 Buchanan's illustration as very much longer than I can find it in any specimen in the 

 College Museum, and styled "the short [sic], slender, or gracilis processus of the mal- 

 leus." Here is a great confusion of terms, as other anatomists make the "long" and 

 " gracilis " process synonymous ; then, too, the expression " long handle " is very vague. 

 Hunter (Phil. Trans. 1787) merely says that the process from the membrana tympani is 

 inserted " into that bone " (*. e. the malleus), and speaks of the other process, that is the 

 bony attachment of the malleus, without naming the homologies of those parts of the 

 ossicle in question. Home (Phil. Trans. 1812) figures the ossicles very correctly, but calls 

 the manubrium the " short handle," and the processus gracilis the " long handle." 



But when we come to compare once more the process connecting the malleus to the 

 tympanic bone in Balcena with the more typical malleus of Felis (PI. LXIII. fig. 14), we 

 shall find that, more strictly speaking, the anterior splint (fig. 13, pg) is the homologue 

 of the processus gracilis, whilst the posterior (phm) is the prolongation towards it from 

 the head of the malleus seen so frequently in terrestrial mammals ; then the floor of 

 thin bone between them (I) represents the lamina (fig. 14, I) of the Carnivora, Ruminants, 

 &c. The whole of the above connecting process between the malleus and tympanic bone 

 is rather longer in Balcena, and perhaps in Balcenoptera, than in the Dolphins and 

 Ziphioid Whales. 



In its large excavated head and short curved manubrium, the malleus of Balcena bears 

 a distant resemblance to the same in Macrorhinus and Stenorhynchus among the Seals. 



* ' Physiological Illustrations of the Organ of Hearing.' London, 1828. 



