546 



ME. D. W. DEVANESEN ON THE 



during the time of croaking (text-fig. 14). When at rest, this 

 part of the muscle is withdrawn and stowed away in a con- 

 spicuous double fold above the anterior portion of the same 

 muscle. 



On removing the suh-maxillaris and the suh-hyoideus several 

 inner muscles of the floor of the mouth come into view (text- 

 fig. 15). It is seen that the transverse fibres of the sub-men- 

 talis (S.M.) pass from the inner border of one mentomeckelian 

 to that of the other, thus having apparently* no connection 

 with the dentary. It is also seen that a greater part of the 

 same muscle is connected with the cartilaginous piece borne by 

 each mentomeckelian, which has been already described in the 

 section on the axial skeleton. Of greater interest is the genio- 

 hyoideus muscle, whose origin and insertion are very different 

 from what obtains in Rana. The outer portion of this muscle 



Text-figure 14. 



A male Cacojans with the vocal sac in action ; drawn from life ; half natural size. 

 The enormous distension of the vocal sac is remarkable ; under natural 

 surroundings it looked more like a float than a resonator. 



arises from the angulosplenial and passes on the outer side of 

 the mentomeckelian cartilaginous piece and that of the sterno- 

 hyoideus muscles to be insei-ted on to the posterior cornu (text- 

 figs. 15 & 16 A). Though it is widely separated from the inner 

 division, it is connected with the latter by some of its fibres, 

 which diverge from its body at about the place of origin and 

 become confluent with the same inner portion, so that on the 

 right side of the toad this outer portion and that part of the 

 corresponding inner division lying in the pre-hyoid pai-t of 

 the floor of the mouth have together the shape of the letter IS". It 

 will be noticed that a few of the connecting fibres are intercepted 



* It looks as though the cartilaginous part of the mentomeckelian has insinuated 

 itself across the fibres of this muscle ; for one finds between the outer side of this 

 same part of the lower jaw several muscular fibres which I presume belong to the 

 suh-mentalis (text-fig. 15, F.M.). 



