706 MB. X. M.V> NEKS-SMITH OX THE [Dec. 4, 



Pectineus. — There are two pectinei, au internal and an external. 

 The internal arises from the lesser spinous process, as it is called by 

 Owen. The muscle is inserted into the femur just below lesser 

 tuberosity and close to the obturator externus. It is supplied by 

 the obturator nerve. The pectineus externus arises from the 

 pectineal spine (greater spinous process of Owen). It is inserted 

 into the femur halfway down the shaft. 



Obturator externus. — Occupies the usual situation. At first sight 

 it appears to be divided into a superior and an inferior portion. 

 Superior portion is more probably inferior gemellus, or, since it 

 receives two branches from the same nerve, it may represent 

 inferior gemellus and quadratus femoris. Its origin, too, would 

 correspond in position to the combined origin of those muscles. 

 The two parts of the obturator externus are easily separated at 

 their origin, but not so at their insertion. The inferior portion is 

 supplied by obturator nerve ; the superior by two fine twigs from 

 that branch of great sciatic which supplies adductor magnus in 

 part and semimembranosus '. Quadratus femoris is present in 

 Echidna and appears to have a similar origin and insertion to the 

 muscle described as superior part of obturator externus. The 

 muscle is most probably combined quadratus femoris and gemellus 

 inferior. 



Obturator internus is absent. The muscle which occupies the 

 usual situation of origin of this muscle is one of the ischio-caudal 

 muscles. Coues describes three ischio-femoral muscles in the 

 region of externus, a, b, and c : a, and probably b, he considers 

 represent obturator externus ; c he considers represents obturator 

 internus. 



Hamstring Muscles. 



Semi-membranosus. — This is a fairly large muscle arising from 

 the tuber ischii. It is situated between the muscle representing 

 semi-tendinosus and biceps above and the adductor group below. 

 It is inserted into the inner side of the head of the tibia. The 

 chief nerve-supply is from the sciatic, the nerve reaching the 

 muscle on its superior surface. There is, in addition, a very 

 slender branch of the obturator nerve, which supplies the inferior 

 posterior portion of the muscle ". 



Semi-tendinosus, with which biceps appears to be blended, is 

 a large sheet which arises by a narrow tendon from the tuber 

 ischii. The muscle spreading out is inserted by its anterior fibres 

 into the expanded upper extremity of the fibula and into a strong 

 tendinous band which passes from this process to patella. These 

 portions most probably represent biceps ; the posterior part becomes 

 thin and apneurotic and is inserted into the crest of the tibia. 

 Coues describes this muscle entirely as biceps, looking upon semi- 



1 Macalister mentions a large gemellus ('Vertebrate Morphology'). Meckel 

 says they are both absent in Ornithorhynchus. 



2 It appears to have very much the same attachment and position in Echidna 

 (Mivart, lor. cit.). 



