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Show 840 ON THE ANATOMY OF PIPA AMERICANA. [Dec. 3, The quadratus femoris is a small slender muscle, covered by the biceps, exactly beneath which it lies. The accompanying drawing (fig. 5) of the muscles visible in a dissection of the outer side of the thigh shows two which I identify with the pyriformis and obdurator respectively. The semimembranosus is a very stout muscle. The psoas is also well developed. I could not find a pectineus, unless what I have called the adductor brevis be really that muscle *? But I do not think, after a comparison with Rana guppyi, that I have made this mistake. The gastrocnemius is a very stout muscle, which arises by a short strong tendon from the femur only. At the ankle it passes into the strong sesamoid bone, well known in the C o m m o n Frog ; perfectly continuous with the latter is a flat strap-shaped tendon, which immediately divides into two divergent tendons, which go to be inserted upon two cartilages which are attached below the heads of the first and fifth metatarsals respectively. The two tendons are united for their whole length by a thin tough fascia. The two tendons and the uniting fascia apparently correspond to the plantar fascia of the frog. But in Rana guppyi, at any rate, the fascia is evenly stout throughout, and does not strip off in the same way because muscles are attached to it. The tibialis posticus does not differ in essentials from Ecker's account of that muscle in the C o m m o n Frog ; but neither in Pipa nor in Rana guppyi does the origin of the muscle extend along the whole length of the tibia ; there is a considerable area at the upper end free from it. The tibialis anticus also needs no comment, save that the division into two bellies is higher up the leg than in Rana guppyi. The peroneus is well developed. So also is the extensor cruris; both these muscles are much as in Rana. The flexor tarsi anterior consists in Pipa of a stoutish muscle, which arises from about the middle of the tibia. The flexor tarsi posterior has no extensor of the middle toe attached to it as in Rana. § Summary of the principal Differences in the Musculature of Pipa and Eana. The following muscles, which are present in Pipa, are wanting in Rana:-(1) Pedoro-mandibular. (2) Abdominal portion of latissimus dorsi. (3) Pulmono-cesophageal. The following muscles, which are present in Rana, are wanting in Pipa :-(1) Rhomboideus. (2) Omohyoid. (3) Pectoro-cutaneus. (4) Sartorius. (5) Pectineus. (6) Branch of posterior extensor tarsi to third toe. Other points of difference are :- (1) Origin of depressor mandibular from skull-wall in Pipa instead of from fascia covering neck. (2) Small size of clavicular |