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



spine, depressed against the side of the ossicle (Globiocephalus, Lagenorhynchus, Pho- 

 ccena) ; or the spine may he well developed and directed downwards, away from the rest 

 of the malleus ( Orca, Pseudorca). Part of the process from the membrana tympani is 

 inserted along a narrow groove on the tubercle. Monodon differs from other Dolphins 

 in the characters of its articular surface, and the length of the head and tubercle of the 

 malleus. 



VIII. All the Dolphins agree in the characters of the incus, which has an ill-developed 

 body and processus brevis, but a very large stapedial crus. The stapes, too, is very 

 similar in character in all these Cetacea. 



IX. Platanista differs remarkably from the true Dolphins in the great length of the 

 process from the head of the malleus, as well as in minor particulars. Such distinctions 

 are hardly perceptible in Inia. 



Appendix to Remarks on Cetacean Ossicula. — The malleus of a foetal Balcenoptera 

 sibbaldii in the Museum of the University of Edinburgh bears a long process in front of 

 the head, with the same homologues, apparently, as are seen in Megaptera. Whether 

 or not this process is arrested, whilst the head increases during the growth of B. sib- 

 baldii is a question only to be solved by the examination of the malleus in an adult of 

 this species. If the process remains long, then it is truly remarkable, since it allies this 

 Balcenoptera to the genus Megaptera, and separates it from B. rostrata and B. huttoni. 

 The incus from the same fetus is of the Balcena type, as the body is very well deve- 

 loped, the long crus by no means so large as in Balcenoptera rostrata. For this observa- 

 tion I am indebted to the kindness of Prof. Turner. I may further add that the malleus, in 

 the skeleton of Macleayius (Bubalcena) australis at the British Museum, is of the Balcena 

 type. 



The OssicuiiA of the Sirenia. 



On account of their large size and conspicuous peculiarities, the ossicula of the Dugong 

 and Manatee have already become familiar to most comparative anatomists; and, 

 through their great durability, even the same bones in Bhytina and Salitherium have 

 been described respectively by Claudius * and Krauss f ; but the most prominent cha- 

 racters which have rendered them interesting to zoologists are due to their structure and 

 consistence, the homologies of their various segments and processes being, on the whole, 

 much easier to distinguish than is the case with the ear-bones of the Cetacea. 



The malleus of the Dugong (Salicore australis, PI. LXIII. figs. 26, 27) is a heavy 

 bone, weighing on an average 40 grains, and measuring about an inch from the root of 

 the processus gracilis to the tip of the manubrium ; the largest specimen never attains 

 the size and weight of the malleus of species of either Manatus or Bhytina, though, from 

 Krauss's account, it appears to be longer than in Halitherium schinzi. 



It is important to bear constantly in mind the position of this bone in the Sirenian tympa- 

 num. In ordinary mammals the head of the malleus lies far back in the tympanic cavity, 



* " Das Gehororgan von Bhytina stelleri," Mem. Acad. Imp. des Sciences de St. Petersbourg, 1867. 

 t Leonhard u. Bronn's N. Jahrb. 1862, p. 385. 



