18 MR, F. E. BEDDARD ON THE [Jan. 14, 



muscles : it is only when they diverge a little to the inside of the 

 mandible that they can be distinguished. In front of this lies 

 the suhmentcdis which has quite normal relations. In addition 

 to these three muscles of the throat which are quite as recognisable 

 in Rana, Brevic&ps possesses another small muscle which is not 

 visible in a corresponding dissection of Rana. This is seen on 

 one side on the right (text-fig. 3, x), running along the inside of 

 the jaw as a fairly broad slip of muscle passing out of sight just 

 behind the submentalis. Between the svibhyoideus and the wall 

 •of the skull and the articiilation of the mandible, there is a 

 considerable space left which is not occupied by muscle. It is 

 filled with a loose tissue which I have not investigated farther. 

 In it, however, lies a large circular flattened and somewhat 

 muffin-shaped body which I take to be the thymus gland, on 

 account of its genei'al (though not minute) agreement in position 

 with the thymus of Rana. 



§ Muscles of Shoulder- girdle * . 



The latissimus dorsi is not a large muscle, and it is entirely hidden 

 for the whole of its course by the miascular origin of the ohliqui 

 ■externujs et internus. And these latter muscles are too thick to 

 allow of the latissimus dorsi being seen through them ; they have 

 to be dissected away to bring that muscle into view. Not only 

 is the latissimus dorsi a small muscle relatively speaking, but it 

 extends for a much shorter way backwards than in Rana, owing 

 perhaps and partly to the very forward position and the small 

 size of the suprascapula. The latissimus dorsi does not at all 

 overlap the infraspinatus. 



The C'ucullaris does not cover the occipital region of the 

 longissimus dorsi as is the case with Rana giippyi ; nor has it so 

 straight a course from the occiput to the border of the supra- 

 scapula. Furthermore it skirts the curved dorsal border of the 

 suprascapula to be inserted into the posterior angle of that 

 ■cai'tilage. 



The retrahens sca2ndce belongs in this Anuran to the serratus 

 (or transverso-scapidaris) series, that is to say it arises from 

 transverse process and not from spinous process. It is necessary 

 to emphasise this point because I have shown that in Rana 

 guppyi this muscle does so arise, and we may therefore fairly 

 speak of it as a rhomboideus . I take this opportunity of con- 

 firming that fact on the results of the dissection of another 

 individual. But whether Breviceps can be said to possess this 

 muscle is a matter open to dispute. In Rana {cjuppyi as well as 

 ■esGxdenta) there are three mviscles which have been termed serrati, 

 but which in Haslam's edition of Ecker (made use of by myself 

 in the preparation of the present communication) are described 

 as transverso-scapidaris. Of these muscles two are broad and flat 



* The pectoralis as well as the omoabdominal are described under the ventral 

 musculature on p. 22. 



