1867.] MYOLOGY OF IGUANA TUBERCULATA. 785 



Supinator accessorius (fig. \2,S.A.). Another muscle, which I 

 also provisionally distinguish by a new name, arises from the internal 

 condyle immediately below, but somewhat superficial to the pronator 

 accessorius. It expands as it descends, and is inserted into about 

 the proximal half of the ulnar margin of the ulna. 



The pronator quadratus (figs. 11 & 12, P. Q.) is broadest below, 

 and becomes very narrow towards its upper end. It arises from the 

 flexor surface of the distal half of the ulna and from the whole radial 

 margin of that bone, and it is inserted into the flexor surface of the 

 radius. 



Flexor carpi ulnaris (figs. 1, 6 & 9, i^. U., and fig. 12, F. C. U.). 

 This forms a large muscular sheet, which, as usual, has the ulnar 

 nerve passing between its double origin — that from the internal 

 condyle and that from the olecranon. It is inserted into both the 

 pisiforme and fifth metacarpal, as Meckel observes*. This muscle 

 receives on its postero-external side the insertion of the extensor 

 carpi ulnaris, the two together forming a layer of muscle which 

 wraps round the ulnar side of the forearm. 



The fiexor sublimis digitorum (fig. 6, F. S. D.) is a thin muscle 

 entirely confined to the handf. It arises from the annular ligament, 

 and is inserted into the second phalanges of the digits, being perfo- 

 rated in each case by a tendon of the flexor profundus digitorum. 



Flexor profundus digitorum (figs. 6 & 12, i^. P. D.). This is a 

 very thick muscle, and has four, more or less distinct heads of origin. 



The first head arises from the internal condyle, immediately beneath 

 the origin of the flexor carpi radialis ; it very soon unites with the 

 portion arising from the ulna (fig. 6, F.P.D. 1). 



The second head also springs from the internal condyle, just below 

 the first head ; it also joins the portion arising from the ulna (fig. 6, 

 F. P. B. 2). 



The third portion takes origin from the greater part of the flexor 

 surface of the ulna. 



These three portions unite and give rise to a very strong tendon 

 (in which is a palmar ossicle) ; and into the deep surface of this 

 tendon are inserted muscular fibres, which spring from the carpus 

 and constitute the fourth head of the muscle. 



From the distal margin of this tendon proceed the five perforating 

 tendons, one going to each digit. 



Lumbricales. I have only observed six lumbrical muscles : — 



One going from the ulnar side of the index tendon to the ulnar 

 side of the second digit. 



Two from the tendon of the third digit (one on each side), in- 

 serted into each side of the third digit. 



Two from the tendon of the fourth digit (one on each side), in- 

 serted into each side of the fourth digit. 



One from the radial side of the fifth digit, inserted into the radial 

 side of the same digit. 



Interossei. There are dorsal interossei which arise from the car- 

 pus, and are inserted one on each side of the proximal phalanx of 

 * Loc. cit. p. 383. t Meckel, loc. cit. p. 392. 



