Mar., 1903.] Spelerpes longicaudus. 3^5 



Musculature. — A careful comparison of the muscles of this 

 stage of Spelerpes longicaudus with the musculature of Rana and 

 Cr\ptobranchus seems to show a close resemblance to Crypto- 

 branchus, especially in the muscles of the branchial apparatus. 

 Of course, no homologues of these muscles appear in the adult 

 Rana, but even the larger head muscles correspond much more 

 closely with those of Cryptobranchus. There appears to be no 

 special modification for sucking, or any special muscles for that 

 purpose. All of the muscles described are those of the adult 

 Salamander in various stages of development. In the nomencla- 

 ture of the muscles of the branchial apparatus, the analogies of 

 Cryptobranchus have been very closely followed out. 



MUSCLES OF THE HEAD. 



M. Temporalis. — (Plate ii. Fig. i, mtm.) The temporalis 

 is the most prominent of the muscles of the head. It arises on 

 the quadrate cartilage, just posterior to the second foramen, and 

 is inserted on the inner side of the coronary process. It is a 

 broad, heavy .sheet of fibres, broader at the insertion than at the 

 origin. Its direction is ventral and slightly caudal. In reality, 

 M. temporalis is made up of two parts, the one just described 

 above, and a second, which I .shall describe as — 



M. Pterygoideus. — This is a thin strand of fibres arising on 

 the quadrate bar, just below the origin of M. temporalis, and 

 sending its fibres ventrally to unite with those of the temporalis. 

 It corresponds very closely to the similar muscle in Cryptobranchus, 

 which is described as follows: "This is a very insignificant 

 muscle * * * and might almost be considered a fasciculus of 

 M. temporalis. (Thesis, J. H. McGregor.) The muscle is 

 entirely covered dorsally by M. temporalis, and acts with the 

 temporalis in lifting the mandible, in opposition to the action of 

 M. depressor maxillae inferioris. 



M. Masseter. — (Plate ii, Fig. i, mm.) The ma.sseter is a 

 heavy, bulging muscle, partly covering M. temporalis. It arises 

 on the anterior third of the auditory capsule, and, running down- 

 ward and forward, is inserted on the outside of the mandibular 

 bar (Meckel's cartilage), a short distance in front of the coronary 

 process. The insertion of this muscle is comparatively very 

 broad, though it is thick-bellied and rounded in the center. 



M. Depressor maxillae inferioris. — (Plates ii. Fig. i, 

 mdm.). This is a large and powerful muscle, which, using the 

 base of the lower mandible as a lever, depresses the jaws. It has 

 two origins ; the first in the middle of the optic capsule, just 

 posterior to the origin of M. mas.seter, and a second, which is 

 lower and posterior to the first. The fibres from the two origins, 

 however, soon intermingle, and evidence of the double origina- 

 tion is lost. The muscle extends down and forward, parallel to 



