1890.] HELODERMA SUSl'ECTUM. 1"! 



ulnar side. To speak more strictly, this superficial muscle of the 

 forearm does not altogether run down its outer side, hut rather 

 crosses the limb somewhat obliquely, from the proximo- radial side 

 to the ulno-distal aspect. 



43. Fled'or carpi radialis. — This rather slender muscle, though it 

 develops a strong tendon both at its origin and insertion, arises from 

 the internal humeral condyle, and, passing down superficially, on 

 that side of the forearm, it becomes inserted into the os carpi radiale, 

 and furthermore sends a tendinous slip to be inserted into the 

 proximal extremity of the pollex metacarpal. 



44. Tlie Pronator radii teres is a conspicuous muscle of some 

 considerable bulk, which arises from the internal condyle of the 

 humerus, by means of a strong tendon, and is inserted into the 

 anterior surface of the shaft of the radius for fully half its length. 

 It is fleshy at its insertion, and intimately related to the Jiexor carpi 

 radialis for its entire length. 



45. Pronator accessorius. — Mivart found this interesting muscle 

 ])resent both in the Iguana and in Parson's Chamseleori, but according 

 to Sanders it is absent both in Liolepis and Platydactylus, and 

 J) resent in Phrynoaoina. Hoffmann states that it is absent in Gonio- 

 cephalun, and he terms the muscle the M. ulno-curpalis. Riidinger 

 termed it the Pronator quadratus proprius ; Mivart gave it the name 

 here adopted ; it is the Pronator radii brevis of Sanders, and the 

 Ulno-navicularis of Fiirbringer. Heloderma susptectum lias it arising 

 from the anterior aspect of the internal condyle of the humerus by 

 rather a slender tendon, whence it passes directly across to the radius 

 to make a carneous insertion upon rather more thnn the middle third 

 of the shaft of that bone, along a line upon its inferior aspect. The 

 tendons of the biceps and the hrachialis anticus pass between this 

 muscle and the proximal third of the shaft of the radius, to their 

 insertions. 



46. Pronator quadratus. — Having removed the superficial layer 

 of muscles from the anterior aspect of the forearm, we readily expose 

 the present one. It is seen to be a fleshy plane of muscular fibres 

 which obliquely span the inter-radio-ulnar space ; arising from a line 

 extending down the shaft of the ulna on its radial side, these fibres 

 pass forwards to the radius and insert themselves on the entire length 

 of its shaft, on the side opposite the ulna. 



Heloderma smpectum, then, possesses all three of these pronator 

 muscles in its forearm, but we see from what has gone before that 

 some lizards may have but one of them, others only two, and still 

 others all three : so, then, we may judge that when the morphology 

 of these Vertebrates is better known, these differences may come into 

 play, as one good set of characters, in their classification. 



At the postero-exterual aspect of the distal end of the ulna, at the 

 back of the carpus, there is fouud in Heloderma a concavo-convex 

 bonelet which I take to be the "pisiform." Attention is drawn to 

 this ossicle here as we shall have to refer to it iu the description of 

 our next muscle. 



4 7. Flexor perforans diyitorum. — -Before rendering ray account 



