186 DR, R. W. SHUFELDT ON [Apr. 1, 



gluteal muscles ascribed by Mivart to Parson's Chameleon ; but as 

 the comparative anatomy of the gluteals is still in a very unsatis- 

 factory condition in so far as their exact determination is con- 

 cerned, and as this is a short adductor, pure and simple, I prefer 

 to provisionally bestow the above name upon it. It both arises and is 

 inserted by tendon, while otherwise it is a short flat muscle of 

 nearly miiform width, which has its origin upon the pubis, anterior 

 to and above the acetabulum, from whence it passes directly to the 

 anterior margin of the great trochanter of the femur, where it is 

 inserted. 



93." Adductor longus. — Here we have another one of the deep 

 muscles of the thigh, being situated on its autero-inferior aspect. 

 Api)arently it arises entirely from the ilio-ischiadic ligament, which, 

 however, is at this point strongly connected to the ischium. At 

 first flat and thin, its fibres soon converge as they descend to their 

 insertion, which is found upon a longitudinal line occupying the 

 lower two thirds of the shaft of the femur, on its ventral aspect. 

 This muscle seems to correspond very well with the "adductor- maffnus" 

 of Mivart, as that distinguished anatomist describes it in the Iguana 

 (P. Z. S. 1867, p. 791). 



94. Vastus externus. — A number of Lizards have the vasti muscles 

 very small, while here in Heloderma they are of considerable size. 

 The vastus externus in the reptile before us is barely one fourth as 

 large as the v. internus. It arises from the anterior aspect of the 

 shaft of the femur, covering its middle third and a portion of its lower 

 third ; below, it becomes tendinous and merges with the tendon of 

 the common extensor of the leg upon the thigh. 



95. Vastus internus. — Comparatively, a great bulky muscle, that 

 covers the shaft of the femur, from which it arises, from head to 

 condyles, upon its antero-posterior aspect. As in the case of the 

 vastus externus, its strong tendon below blends with the tendon of 

 the rectus femoris, while the two vasti muscles themselves are prac- 

 tically almost fused into one. 



90. Pyriformis. — The muscle I take to he the present one in Helo- 

 derma makes quite a remarkable departure from the pyriformis as it 

 occurs in other Lizards. Indeed, it might here almost be called an 

 accessory femoro-caiidal in some particulars, as our description will 

 go to show. The main part of the muscle arises fleshy from the ven- 

 tral surface of the diapophysis of the first caudal vertebra, encroaching 

 slightly upon the centrum of the bone. The fibres converge and are 

 directed down the back of the thigh. As they come to an apex, this 

 apex is joined by a small axillary muscle that arises from the tendinous 

 arch of the ilio-ischiadic ligament. Together the muscles at once 

 unite to form a delicate tendon, which, in its course towards the head 

 of the tibia, is closely juxtaposed to the tendon of the /eworo-cflMi/a/ 

 or rather to its branch tendon. At the lower third of the thigh 

 this tendon of the 2ryriformis and the branch tendon of the 

 femoro-caudal fuse into one cord, which is inserted into the tendon 

 of the external head of tlie gastrocnemius muscle a iew millimetres 

 below the insertion of the latter into the external condyle of the femur. 



