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Show 1890.] HELODERMA SUSPECTUM. 187 In sequence with it, the above-mentioned larger part of the pyriformis seems to be the continuation forwards of the cloacal muscle, of the infracaudal group of muscles. In different forms of Lizards we find the pyriformis muscle very differently constituted, and consequently very different descriptions of it extant ; so when we come to consider the diverse nomenclature that has been awarded to it, the question of its study becomes quite puzzling. For instance the pyriformis of Sanders is said by Hoffmann to be the femoro-caudal of Mivart, while Hoffmann himself has called it the M. coccygeo-femoralis longus s. Pyriformis ; while on the other hand the pyriformis of Mivart is the coccygeus inferior of Sanders, the M. coccygeo-femoralis brevis of Hoffmann, and which is the subcaudalis oi Stannius. I still believe that the myology of reptiles demands fuller research at the hands of anatomists. 97. Coccygeus inferior.-A muscle which arises by a thin sheet of tendon from the haemapophyses of the second, third, and fourth caudal vertebrae. Forming anteriorly a delicate slip of muscle, it is inserted into the ischium just posterior to the acetabulum. The coccygeus inferior lies to the inner side of the femoro-caudal, that is, it is mesiad to it, while the point of its insertion is internal to that of the obturator externus. Sanders found this muscle present in Liolepis, where it arises from the extremities of the haemal spines of the caudal vertebrae from the tenth to the third. 98. Coccygeus externus.-Arising from the ventral aspects of the diapophyses of the second and third caudal vertebrae, this laterally compressed muscle passes directly downwards and slightly forwards to insert itself powerfully into the ilio-ischiadic ligament. It will be noticed that this muscle lies almost in the same plane with the pyriformis in front and the cloacal muscle posterior to it, the three being in sequence, their apposed margins in contact, and the whole situated to the outer side of the femoro-caudal. Phrynosoma possesses the coccygeus externus as is stated by Sanders. 99. Obturator internus is a large and powerful muscle in Heloderma suspectum, arising from the pubis and ischium at the ventral aspect of the pelvis. These fibres of origin start mesiad from the symphysial line, and, converging to some extent and becoming slightly tendinous, they are attached, by an extensive insertion, upon the summit of the shaft of the femur, on top of the trochanter major. The muscle as thus constituted is thick and covers over nearly all of the ventral aspect of the pelvis in front of and immediately beneath the acetabulum ; the iliacus covering a strip along and beneath the pubis anteriorly. 100. Obturator externus.-With a bulk that is barely one third of that of the obturator internus, the present muscle arises, tendinous, from the tuberosity of the ischium, posterior to and below the acetabulum. Forming a strong, thick bandit passes round the summit of the femur to make insertion by a powerful tendon at a point upon the proximal end of the shaft just below the caput femoris, upon the posterior aspect. This point is separated from the insertion of the obturator internus by a space of some three millimetres, the two in |