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Show 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 m y 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 m 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 m y paper on L. belli, and also in fig. 17 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 represented, 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 posterior 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 correspond to the first part of the iliacus in Iguana. Obturator interims 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 quadriceps 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 |