1908.] ANATOMY OP A FROG. 13 



perhaps, with the unusually strongly developed subhyoideus 

 muscle. Again, correlated with these facts of structure is the 

 mode of origin of the anterior cornua from the body of the hyoid. 

 As the text-figure referred to shows, the anterior cornu on each 

 side bifurcates near to its junction with the body of the hyoid, 

 and shortly afterwards the two branches rejoin, thus forming an 

 almost triangular foramen. Anteriorly there is no distinction 

 between the cornu itself and the anterior process of the body of 

 the hyoid, such as is so marked in Eana. In fact, the connection 

 of the anterior cornua of the hyoid with the basihyal recalls the 

 arrangement of the corresponding cartilages in the not nearly 

 allied Pelodytes, but more so as there is a close approach in the 

 middle line between the rounded-ofF ends of the conjoined 

 anterior process and anterior cornu of either side ; they do 

 not, however, so nearly meet in Breviceps as is the case with 

 Pelodytes. 



The figures of the hyoid apparatus of other Frogs given by 

 W. K. Parker* show no types which closely resemble Breviceps 

 in these particulars. In many forms, however, there is no 

 anterior process on either side of the basihyal, and in others 

 there is an approximation between the anterior lateral process of 

 the basihyal on each side and the corresponding cornu. The 

 thyrohyals of Breviceps are also peculiar in certain respects. 

 Each is ossified as usual and is of the customary hourglass-shape, 

 being — that is to say — thinner in the middle than at its two ends. 

 It is, moreover, rather bent in the middle outwardly. The end 

 by which it articulates with the body of the hyoid is not affixed 

 iio that cartilage as in many (? most) Frogs. In the latter the 

 bone is inserted on to the posterior edge of the basihyal cartilage. 

 In Breviceps it is quite distinctly inserted on to the ventral 

 surface of the cartilage in front of the posterior edge t. 



§ The M'USGidature of the Hyoid. 



As might be expected from the habits of the Frog, the Hyoid 

 muscles differ in many respects from those of Rana, &c. I shall 

 describe under the heading of the abdominal muscles an important 

 muscle which I term Jiyoahdominal, which is a part of the superficial 

 abdominal sheath inserted on to the hyoid. 



The sternohyoid is also a peculiar muscle. For it is composed 

 of two perfectly distinct parts. The anteriorly attached part has 

 the usual insertion on to the body of the hyoid ventrally between 

 the (posteriorly) diverging halves of the geniohyoideus of its 

 side. This part of the sternohyoideus arises almost entirely 

 from the coracoid dorsally ; the second half of the sternohyoideus 

 is in contact at its origin with the last, and appears also to be 

 continuous with such fibres of the very feeble rectus abdominis 



* Phil. Trans, pt. i. 1881. 



f Parker's figure of Eiigystoma carolinensis suggests that this is also the case 

 with that species, which is of the same family. 



