1908.] ANATOMY OF A FROG. 21 



wards and which arise from the middle line of the back, ?'. e. from 

 the spinous processes of the vei'tebraj. These fibres are continuous 

 with some of those upon the ventral surface which I have shown 

 reasons for believing to be the ohliqvMS externus of Rana. 

 Immediately beneath them, and equally plainly shown in the 

 drawing (text-fig. 4), is a set of fibres, also arising from the 

 spinous processes of the vertebrfe, which run diagonally to the 

 former and are in fact disposed at I'ight angles to the longitudinal 

 axis of the body. These are of course the fibres of the ohliquus 

 internus. I imagine tha't these two muscles together in their 

 dorsal region represent the fascia dorsalis of Rana. In any case, 

 apart from any question of homologies, it is remai-kable to have to 

 note the extreme muscularity of the back of this small burrowing 

 toad when compared with Rana. This sheet of muscle completely 

 covers the latissimus dorsi, but it only pai'tly covers the infra- 

 spinatus, the anterior half of which appeal's, as is shown in the 

 drawing (text-fig. 4), beyond its anterior margin. In this 

 region, in fact, it passes into an aponeurosis. A striking feature 

 of the dorsal musculature of this Frog as compai-ed with Rana, is 

 the absence of a depressor mandihidoi. Hence the suprascapula 

 is visible directly the skin is raised. In view of the presumably 

 feeble action of the jaws in this ant-eating toad, the absence of 

 this muscle is not surprising. Posteriorly the obliquus internus 

 ends abruptly at the commencement of the posterior lymph- 

 heart *. At that point the longissimus dorsi emerges from beneath 

 its shelter, and is seen to arise from the coccyx to very far back, 

 in fact within a millimetre of its posterior extremity. This is 

 quite diflerent to what occurs in Rana., where the greater part of 

 the coccyx is free from the longissimus dorsi. It may perhaps 

 be ai-gued from this fact, coupled with the fact that the end of 

 the coccyx is a long way from the anus, that Breviceps is as com- 

 pared with Rana a short-tailed frog. It also follows that the 

 insertion on to the coccyx of the ilio-coccygeal muscle is hidden 

 by the longissimus dorsi. 



Since only the extreme tip of the coccyx, represented in the 

 figui'e to which reference has been made, is free from the attach- 

 ment of the longissimus dorsi, it is plain that the cgccygeo-sacralis 

 must be either absent or. have rather different relations. In view, 

 however, of the very large transverse processes of the sacral 

 vertebra? in this Batrachian, the muscle would be hardly likely to 

 be absent, and indeed I identify it as shown in the drawing (text- 

 fig. 4, CocG.Sac). The muscles in question are attached on each 

 side of the body to the strong transverse process of the sacral 

 vertebra. Not, however, to the whole of that process. For the 

 outer part bears the origin of the glutceus. The muscle (the 

 cocGygeo-sacralis) is pyramidal in foi'm ; it nai'rows from its wide 

 origin to the region of the pyi'iformis, up to which muscle it passes, 

 and is attached at the extremity of the coccyx between the origins 



* For the description of which see p. 33. 



