14 MR. F, E. BEDDARD OX THE [Jan. 14,. 



sternalis as reach the stei'iinm. Its direction is from the very 

 first different fi-om that of the anterior portion of the muscle. 

 It passes downwards at a greater angle with the plane of the 

 coracoid and to the inside of the hyoabdominal, dorsally to which 

 it then passes to be inserted opposite to the insertion of the 

 outer pai-t of the geniohyoid. The hyoabdominal thus passes- 

 between the two portions of the sternohyoid, and it is able to- 

 insinuate itself into the narrow space prepared for its reception, 

 not by a diminution of its fibres or a lessening of its diameter by 

 becoming converted into a tendon, but by bending over so that 

 its broad and flat surface comes to be disposed perpendicularly 

 instead of horizontally. 



The geniohi/oideus of Breviceps appears to offer no very great 

 difi"ei'ences from the same muscle in Rana. But the two inner 

 halves of the two muscles fuse together some Avay back over the 

 subjacent hyoglossus more markedly than in Rana, and in this^ 

 the muscle recalls the geniohyoid of the Pelobatidae *. 



I could find no trace whatever of an omohyoid muscle. 



The hyoglossus completely envelops each thyrohyal. The fibrea 

 run aggregated into coarse strands over the hoAj of the hyoid. In 

 the region of the thyrohyal the hyoglossus is overlain by a thin 

 layer of muscle which appears to be perfectly continuous with the 

 geniohyoid (see text- fig. 7, A, p. 28), that is of course with the inner 

 division of that muscle. The fibres, however, are here transversely 

 ari-anged to the longitudinal axis of the thyrohyal and are wrapped 

 round the enormously thick hyoglossus. In view of their direction 

 these fibres can hardly be referred to the geniohyoid and called 

 by its name ; but they appear to be clearly a differentiation of 

 the same sheet of muscle. The function of this sheet of muscle 

 appears to me to be possibly this : the enormously develojDed 

 musculature — the hyoglossal — which enwraps each ceratohyal 

 tends to occlude, particularly during its contraction, the glottis, 

 and thus to hinder free respiration. This would, however, be- 

 advantageous during swallowing. During relaxation of the 

 hyoglossal the diameter of that muscle would, perhaps, be still 

 further reduced by the conti'action of the transverse sheet, and 

 the orifice into the lungs in consequence enlarged. 



The petrohyoid muscles are present in the normal number 

 and are thick and fleshy leaving no gaps, and indeed overlapping 

 each other. The posterior division of the muscle seems to be less 

 attached to the thyrohyal than is usual among these Batrachians. 



The petrohyoideus posterior p>rimus has apparently some con- 

 nection with the bony thyrohyal bar. When the latter is raised, 

 the muscle is seen to underlie it (it is of coin^se dorsal to the 

 bone) and to be posteriorly attached to it. The muscle is, in 

 fact, antei-iorly inserted on to the edge of the body of the hyoid 

 behind the posterior lateral process, this portion of the body of 

 the hyoid being, as already explained, ovei-lain by the thyrohyal 



* See P. Z. S. 1907, p. 895. 



