686 ME. F. E. BEDDARD ON THE [June 16, 



pericardium." These will then form the ventral part of the 

 diaphragm. I do not find after a careful dissection of an average- 

 sized example of Rana esculenta any evidence of a deflection of 

 rectus fibres to the pericardium. I am the more confident in the 

 accuracy of my observation in that I have discovei'ed such a 

 muscle in the small Rhinoderma darivini. This I figure in the 

 accompanying illustration (text-fig. 145). The muscle is thin and 

 wide and flat, and its fibres run accurately in a direction parallel 

 with the long axis of the body. It is attached to a good deal of 

 the posterior and lateral margins of the pericardium. It underlies 

 the obliquus externus behind the sternal region {i. e. is dorsal to 

 it), and is therefore perhaps to be regarded as a portion of the 

 obliquus internus. 



The relations of the suhmaxUlaris are difl'erent to those which 

 obtain in some other frogs. The muscle is, however, similar in 

 that its posterior region is separated ofi" as a distinct muscle, the 



Text-fig. 146. 



Snv. 



SX 



Musculature of floor of mouth of Ehinoderma darwini. 



a. Genioglossus (?). h, c. Differentiated portions of submaxillaris. 

 Sh. Subhyoideus. 8m. Submeutalis. 



subhyoideus. The latter is only plainly difl:erentiated from the 

 formei' near to the edge of the lower jaw, where it dips down to a 

 loM'er plane. Its relative dimensions apjDear to be very much those 

 of the muscle in Rana. Nor is there anything in the structure or 

 size of the submentalis that calls for j)articular comment. The 

 muscle appears to be exactly like that of Rana. It will be noticed, 

 however, in the accompanying drawing (text-fig. 146, a) that two 

 large triangular muscles, one on each side, underlie the submaxil- 

 laris, which muscles are not visible in a corresponding dissection 

 of Rana. ISTor have I seen them in the same place in such 

 Pelobatidse as I have dissected *. These two muscles, as will be 

 seen in the text-figure referred to, are closely approximated in the 

 middle line ; and into the space left by their divergence in front 

 fits exactly the submentalis. 



* On Megalophrys nasuta, P. Z. S. 1907, p. 338, &c., and on Pelobatidse, ih. t. c 

 p. 871. 



