1908.] OF THE BATRACHIAN GENUS HEMISUS. 907 



throat by a considerable tendinous interval anterioi-ly. This 

 non-m\iscular interval diminishes in breadth posteriorly until it 

 practically disappears in the region of the subhyoideus. In 

 addition to this the submaxillaris consists of an anterior layer of 

 fibres on each side which are comparable to an almost similarly 

 placed layer of fibres in Rhinodenna. A thin layer of fibres runs 

 on each side from the fascia covering the submentalis to the ramus 

 of the jaw in an oblique direction, and overlies almost at light 

 angles the section of the submaxillaris which is contiguous. This is 

 clearly shown in text-figure 176, s.m.\ and needs no more elaborate 

 description. 



The subhyoideus is of about the same proportions as in Rana, 

 and passes behind the ramus of the lower jaw on its way to the 

 cornua of the hyoid. That it is attached to the cornua of the 

 hyoid and not to the wall of the skull is quite aj^parent. An 

 examination of text-figure 176 would seem to show an additional 

 muscle belonging to the series which form the floor of the mouth, 

 and arising on either side from the anterior extremity of the 

 sternum. I am unable, however, to give any further details 

 about this muscle than are displayed in that figure. It may of 

 course be merely an anterior slip of the pectoral series (including 

 the sterno-radialis). 



§ Hyoid and, its 2Iusculature. 



The hyoid cartilages of Hemisits are peculiar in several respects. 

 The main features of this part of the skeleton can be understood 

 by a reference to the accompanying text-figures (text-figs. 179, 180, 

 pp. 908, 909). The body of the hyoid is rather long and narrow. 

 The anterior hyoid processes of the body of the hyoid join the 

 anterior cornua much in the way that is to be seen in the hyoid 

 oi Brevicejis * . Furthermore, the two anterior cornua or cerato- 

 hyals themselves join ventrally of the median body of the hyoid 

 and project in the shape of a rather broad plate for some way 

 backwards over the latter. The hyoglossus muscle therefoi-e passes 

 through an actual foramen in the hyoid, which it completely fills. 

 It is evident, however, that this hyoglossal foramen is not absolutely 

 homologous with that of Xenopus t, but is more comparable to the 

 nearly complete foramen seen anteriorly in the hyoid of Pelodytes %. 

 For the foramen in Xenojnts is an actual perforation of the body of 

 the hyoid, whereas in Hemisits the foramen is produced beyond 

 the end of the body of the hyoid and by the approximation of the 

 origins of the anterior cornua of the hyoid. Were there a com- 

 plete foramen in the hyoid of Pelodytes 2^unctatus it would be 

 more comparable to that of Hemisiis in that the anterior cornua 

 enter into its formation. It would not, however, be strictly 

 homologous ; for in Pelodytes and Pelobates there ai'e a pair of 



* P. Z. S. 1908, p. 12, text-fig. 2. 



t See Ridewood, Journ. Linn. Soc, Zool. vol. xxvi. pi. 8. fig. 1, li. 



X Ridewood, P. Z. S. 1897, pi. xxxv. fig. 10. 



