188 MR. A. H. G. DORAN ON THE MORPHOLOGY OF 



JPlatanista is distinguished from the above delphinoid Cetaceans 

 by the great length of the process from the head of the malleus, 

 and by other less conspicuous modifications in that ossicle. 

 Such distinctions are hardly discernible in the genus Inia. 



In the Sirenia the ossicula are modified more in texture, weight, 

 and outline than in the development or suppression of any of 

 their processes as in the Cetacea. Their singular general mo- 

 difications of form mask any points of resemblance to their re- 

 presentatives in any other order which otherwise might be ob- 

 servable, excepting that in Halicore and, apparently, in Halitherium 

 there is an approach to a quadrilateral form of stapes, which at 

 least reminds the anatomist of the form of that bone in the larger 

 Ruminants, In no respect do any of the ossicula resemble those 

 of the Whales and Dolphins. Halicore differs distinctly from 

 Manatus in several particulars, most of which have been already 

 described by Hyrtl. In JRhytina the malleus and incus, judging 

 from the description and figures given by Clausius, very closely 

 resemble those of the Manatee. In Halitherium the description of 

 the ossicula with which Dr. Krauss has favoured science leads me 

 to consider that the malleus is intermediate in type between those 

 of Manatus and Halicore, the incus more resembling that of the 

 former Sirenian. 



In the Bradypodidse, among the Edentata, the characters of the 

 malleus and incus are fairly'generalized, whilst the stapes assumes, 

 to a certain extent, Sauropsidan characters. Among the Arma- 

 dillos the genera Dasypus and Tatusia present much higher cha- 

 racters in the ossicula of adult specimens than can be found in 

 Priodon and Tolypetctes. The malleus in the adults of the two 

 latter genera resemble the same ossicles in the fully developed 

 foetus of Dasypus and Tatusia. This recalls an identical condition 

 in Bos and Ovis. 



In the Manidse the ossicula possess the most positive charac- 

 ters among all the Edentata. The malleus is more specialized 

 than in the other groups, and the stapes is more absolutely 

 columelliform than in any other placental mammal. In the Ant- 

 eaters the malleus may be known from that of other Edentata 

 by the form of its head ; in Gyclothurus it resembles that oi Brady- 

 pus more than do the same bones in MyrmecopJiaga a.n^ Tamandua. 



In Orycteropus the malleus is quite unlike that of any true 

 Ant-eater, but resembles, to a certain extent, that of Priodon, 

 from which, however, it maintains very distinctive features. 



