1908.] ANATOMY OF A PROG. 27 



insertion of this adductor magnus (if I am right in so terming it) 

 did not appear superficially. This variability, it will be observed, 

 is precisely analogous to that exhibited by the constituents of the 

 triceps femoris on the outside of the thigh, which will be presently 

 described. Returning to the muscles visible on the inside of the 

 thigh, the only ones visible without dissection, in addition to those 

 already treated of, are the recti intei'ni major et minor. The 

 connection of the latter with a superficial muscle has already been 

 dealt with. As in Bana the semitendinosus does not appear 

 superficially. 



On the outside of the thigh the most prevalent muscle is the 

 equivalent of the triceps feonoris of Rana, though its constitution 

 in Breviceps differs somewhat. There are, however, three distinct 

 portions which may be termed respectively rectus femoris, vastus 

 externus, and vastus internus. They are, however, all of them 

 inserted separately, instead of by one tendon as in Rana. More- 

 over, the most anterior of the three muscles, the rectits femoris 

 anticus, instead of ending in an aponeurosis, is fleshy and thick 

 throughout. The two specimens which I have dissected show a 

 difference in the insertion of the middle of the three divisions of 

 the triceps femoris. In one this goes as far as the knee ; in the 

 other individual the muscle is inserted on to the thigh up to about 

 the middle of that bone only. It is therefore not only in the 

 separateness of the three divisions of the triceps femoris, but also 

 in their insertion and complete muscularity that Breviceps differs 

 from Rana. The biceps femoris in Breviceps is a particularly 

 slender muscle ending in a long tendon, not flattened, which 

 pushes between the two heads of the gastrocnemius some way 

 after their origins to be inserted a longish way down the fore 

 leg. The semimembranosus is of fair size. 



§ (Esophageo-2yulmona7nj muscle. 



This muscle in Breviceps is a very stout muscle obscvirely 

 divided into three or four bundles which have hardly the value 

 of separate muscles. It has no direct connection whatever with 

 the muscles of the wall of the abdomen. It is not (that is to say, 

 obviously) a detached sheet of the obliquus internus, as is the case 

 with the corresponding muscle in all of the Pelobatidae that have 

 been hitherto examined*. It is in fact similar in many respects 

 to its homologue in the Ranidas and Bufonidse. It arises in them 

 from the transverse process of the fourth vertebra, and this is also 

 the origin of the muscle in Breviceps. Its origin lies in front of, 

 and contiguous with, the insei"tion of the ilio-lumbaris, and to the 

 inside of the origin of the transverso-scapularis. The origin and 

 course of the muscle is shown in the accompanying illusti^ation 

 (text-fig. 7). It nearly meets its fellow of the opposite side of 

 the body in the middle line of the ventral surface of the oesophagus. 



* Beddard, " On Anatomy of a Frog of the genus Megalophrys," P. Z. S. 1907,. 

 p. 324 ; and " On Anatomj^ of Pelobatida?," ibid. p. 886. 



