84 MR. A. SANDERS ON THE [Jan. 6, 



iliacus in Iguana are wrongly so interpreted will appear upon the 

 consideration that they are situated on the outer side of the limb 

 instead of the lower or ventral side, and that the fibres face dorsad 

 instead of ventrad. As the latter muscle arises from the same bone 

 as the iliacus in my specimen, that point need not be discussed. 



Iliacus externus is simply a dismemberment of the iliacus, but has 

 a distinct origin and insertion ; it arises from the whole length of the 

 posterior edge of the pubis, and is inserted into the front part of the 

 trochanter beyond the iliacus and extending between it and the 

 insertion of the pyriformis. It differs from the same muscle in 

 L. belli only in not being connected with the origin of the pelvo- 

 tibialis ; it corresponds with pectineus No. 1 in Iguana. 



Obturator externus arises from the ventral or lower surface of the 

 ischium, extending from the mid line as far outward as the external 

 angle of the same, and is inserted into the posterior and outer surface 

 of the femur, behind the trochanter and close to the head. This 

 nearly resembles the same muscle in L. belli, except that it does not 

 cover the ischio-pubic foramen. This is figured in my paper on 

 L. belli, and also in fig. 1 7 of Mr. Mivart's paper on Iguana. 



The muscles on the dorsal or upper aspect of the ischium and 

 pubis are not so complicated as in L. belli ; neither are they connected 

 in so intimate a manner ; instead of four there are only two muscles 

 in this species, the flexor femoris and flexor tibialis not being repre- 

 sented, or rather one muscle combining the properties of the two ; 

 it may therefore retain the name of 



Flexor femoris (figs. 4 & 5, F.F.). This arises from the inner half 

 of the dorsal surface of the pubis, and from the external half of its 

 ventral surface and also from its anterior edge. The part from the 

 anterior edge becomes merged into the pelvo-tibialis ; while the pos- 

 terior portion is inserted into the anterior and inner surface of the 

 femur close to the head of that bone, passing behind the origin of 

 the rectus and in front of the vastus externus ; this corresponds to 

 the second section of the iliacus in Iguana. A muscle figured in my 

 paper on L. belli, and there termed flexor tibialis, appears to corre- 

 spond to the first part of the iliacus in Iguana. 



Obturator internum arises from the dorsal surface of the whole 

 length of the ischium and from the posterior two thirds of the ischio- 

 pubic ligament ; it passes out of the pelvis behind the last, and ends 

 in a narrow tendon which is inserted into the posterior surface of the 

 femur a short distance from the head ; this corresponds to the third 

 portion of the iliacus in Iguana, while a muscle not found in this 

 specimen, but figured in L. belli under the name of flexor profundus 

 femoris, appears to be the same as the fourth section of the iliacus 

 in Iguana. 



Rectus femoris (figs. 4 & 5, R.F.) in this species has only one 

 origin, from the edge of the pubis in front of the acetabulum ; it ends 

 in the usual manner to coalesce with the two vasti to form the qua- 

 driceps or, rather, in this case, the triceps extensor femoris, and is 

 inserted by means of the ligamentum patellae into the head of the tibia. 



Vastus externus commences in a point close to the head, covering 



