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, T. 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 per- 

 haps 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 profun- 

 dus 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 per- 

 forating tendon of the third and fourth digits, and go respectivelv 

 to the tibial sides of the same digits (fig. 18, X. 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. H.). 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. 



Interossei. 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. 



