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Show 186 DR. R. Vi. 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 unsatisfactory condition in so far as their exact determination is concerned, 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 uniform 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 antero-inferior aspect. Apparently 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 magnus" 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 practically almost fused into one. 96. Pyriformis.-The muscle I take to be the present one in Heloderma makes quite a remarkable departure from the pyriformis as it occurs in other Lizards. Indeed, it might here almost be called an accessory femoro-caudal in some particulars, as our description will <ro to show. The main part of the muscle arises fleshy from the ventral 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 femoro-caudal or rather to its branch tendon. At the lower third of the thigh this tendon of the pyriformis and the branch tendon of the femoro-caudal fuse into one cord, which is inserted into the tendon of the external head of the gastrocnemius muscle a few millimetres below the insertion of the latter into the external condyle of the femur. |
