1890.] HELODERMA SUSPECTUM. 187 



In sequence with it, the above-mentioned larger part of the ^jy/v- 

 /ormis seems to he the continuation forwards of the c/oacaZ mwsc^e, 

 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-cuudal of jNIivart, while Hoffmann himself has 

 called it the M. cocciigeo-femoralis lonc/us 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 of Stamiius. 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 hsemapophyses of the second, third, and fourth 

 caudal vertebrte. 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 

 com|)ressed 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-caudcd. Phrynosoma 

 possesses the coccygeus externus as is stated by Sanders. 



99. Obturator internus is a large and powerful muscle in Helo- 

 derma suspectum, nv'ism^ from the pubis and ischium at the ventral 

 aspect of the pelvis. These fibres of origin start mesiad from the sym- 

 physial line, and, converging to some exteut 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. 

 Tlie muscle as thus constituted is thick and covers over nearly all of 

 the ventral aspect of the pelvis in front of and immediately beneatli 

 the acetabulum ; the iliacus covering a strip along aud 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 ace- 

 tabulum. 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 



