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Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 797 The tibialis posticus is very narrow above and very broad below. It arises from the lower half of the posterior surface of the fibula, and its fibres pass downwards and tibiad. It ends inferiorly in a broad expanded tendon, which is inserted into the posterior process and whole posterior border of that tarsal bone which fits into the concavity on the under surface of the astragalus (figs. 16 & 18, 7'. P.). Peroneo-tibial. A remarkable muscle connects together rather more than the lowest two-fifths of the tibia and fibula. Its fibres pass from the posterior surface and tibial border of the last-named bone to the peroneal margin, and to a very little of the anterior margin of the tibia (fig. 16, P. Tb.). This muscle is unlike any with which I am acquainted, unless it be the very similar one found in the leg of the Wombat. Flexor accessorius. Two small muscular bands, which may perhaps be so named, are thus conditioned : - (1) The first springs from the plantar aspect of the os calcis, and is inserted into the peroneal side of the tendon of the flexor profundus digitorum before its division. (2) The second part from the tibial aspect of the ridge on the plantar surface of the fifth metatarsal, and is inserted into the tendons of the second, third, and fourth digits (fig. 18, F. A. 1 and F.A.2). Lumbricales. I have only detected two muscles which appear thoroughly to answer to mammalian lumbricales. These arise from the plantar surfaces and tibial sides of the perforating tendon of the third and fourth digits, and go respectively to the tibial sides of the same digits (fig. 18, L. 1 and L. 2). Three other narrow flat muscular bands go from the deep surfaces of the perforating tendons of the third, fourth, and fifth digits to the plantar surfaces of the proximal phalanges of the same digits. Abductor hallucis (fig. 18, A. Hi). This is a flat muscular band, which arises from the plantar surface of the naviculare, very near to the proximal end of the first metatarsal, and is inserted into the proximal phalanx of the hallux. The abductor ossis metatarsi quinti (fig. 18, A. Q.) is a similar flat muscular band arising from the distal end of the os calcis, and inserted into the peroneal border of the distal end of a groove on the deep surface of the fifth metatarsal bone. Next the surface of this groove is a strong tendon. Flexor minimi digiti (fig. 18, F. M.). This small muscle arises from the tibial aspect of the ridge on the plantar surface of the fifth metatarsal, and is inserted into the proximal phalanx of the fifth digit. Lnterossei. There are dorsal and plantar interossei in the pes very similar to the corresponding muscular fasciculi of the manus; but besides these there is a superficial layer of plantar muscular fibres. This layer takes origin from the tibial side of the cuboid and fifth metatarsal, and is covered superficially by the second part of the flexor accessorius. Spreading out in a fan-like manner, it is inserted into the three middle digits. |
