74 ANATOMY OF THE WOOD RAT 



M. gemellus superior (figs. 16, 32) arises along the 

 caudal part of the dorsal border of the ilium caudad almost 

 to the acetabulum. Insertion is onto the medial portion 

 of the great trochanter of the femur. 



In Teonoma the muscle is broader but is separable from 

 the gluteus medius only with some difficulty. 



M. pyriformis (figs. 16, 32, 33) is a short muscle lying 

 immediately deep to a part of the gluteus medius and 

 directly over the sciatic nerve. Origin is from the diapo- 

 physes of the first two (?) sacral vertebrae, and insertion 

 is onto the great trochanter of the femur. Contrary to 

 the statement of Parsons (1894, p. 283) the closest rela- 

 tionship of this muscle is with the gluteus medius, and not 

 the gluteus minimus. This is so in the case of the gemellus 

 superior, however, and from his statements as to origins, 

 it seems that he may have confused this with the pyri- 

 formis, overlooking the true pyriformis entirely. 



In Teonoma this seems not to be separable from the 

 gluteus medius with any surety. 



M. obturator internus (figs. 16, 17, 33) has origin 

 from the medial surface of the ischium caudad and craniad 

 of the obturator foramen. It converges and passes over 

 the dorsal border of the ischium between its tuber superior 

 and the acetabulum, and is inserted into the trochanteric 

 fossa. The insertional part of this muscle forms a por- 

 tion of the floor of the intramuscular passage for the sciatic 

 nerve. 



M. gemellus inferior (figs. 16, 17, 32). It is only by 

 its origin that this muscle may be readily distinguished. 

 It arises from the gemellus fossa upon the ischium just 

 craniad of the superior tuberosity, and is inseparably in- 

 serted onto the caudal margin of the obturator internus 

 near its insertion. 



M. quadratus femoris (figs. 17, 32, 33) has origin from 

 the lateral surface of the ischium ventrad and craniad of 



