1 890. J HELODERMA SUSPECTUM. 163 



from these points. Passing downwards and forwards it becomes 

 inserted by a strong tendon into the proximal third of the corre- 

 sponding humerus upon its ulnar aspect. The o\iter margin of this 

 muscle develops a strong tendon, which, as the muscle itself passes 

 between the heads of the triceps to its insertion, branches off to 

 insert itself into the triceps, upon its inner head. Mivart found a 

 similar tendon to this in Iguana, and Sanders in Phrynosoma ; but 

 the latter anatomist found it absent in Liulepis. 



18. Levator scapu/ce. — This is a Hat, triangular muscle that 

 arises fleshy from the external aspect of the anterior part of the 

 scapular and suprascapular, and from the anterior margins of both 

 of these bones. Its fibres converging as they pass directly forwards 

 and passing between tlio deep muscles at the side of the neck, it is 

 finally inserted by a strong tendon into the side of tbe atlas. 



19. Pectoralis. — Heloderiiia has this important breast-muscle 

 well developed ; it arises from the external longitudinal half of the 

 entire length of the interrlavicle, from the posterior border of the 

 inner end of the clavicle, from the ventral aspect of tlie sternum, 

 from the corresponding surfaces of the last four costal ribs and the 

 intercostal fascia, and finally posterior to these parts from the fascia 

 of those muscles of the abdomen which are situated deep to the 

 pectoralis. 



From these several points of orighi, n pectoralis of either side has 

 its fibres converging to a point represented by the tuberosity of the 

 humerus of the same side, and here tliey are inserted, tendinous, 

 upon a line defining its mesial aspect, and for its entire margin. 



20. Deltoideus in tbe species before us arises by two heads — the 

 anterior head from the underside of the mesial extremity of the 

 clavicle ; the posterior head from the interclavicle close to the 

 anterior head, and from the surface of the sternum immediately ad- 

 jacent : these two heads are in coiitact for their entire lengths, aud 

 their fibres are sent directly to tlie corresponding humerus ; passing 

 backwards aud outwards, they become inserted by a strong tendon 

 upon tbe head of that bone, just anterior to the next-to-be-described 

 muscle. It appears that Sanders found in Liolepis aud in Phry- 

 nosoma only that part of the deltoideus which represents its clavi- 

 cular portion present. I believe it has a double head in the Iguana. 



21. The Siipraspinatus is a flat, triangular muscle of the chest, 

 which, in this lizard, arises (Vom the anterior half of the mesial 

 margin of the coracoid, by means of a strong aponeurosis ; the fibres 

 converge as they take their way to the humerus of the same side, 

 and are inserted, tendinous, into the tuberosity of that bone, close to 

 the insertion of the pectoralis. 



Here in Heloderma the supraspinatus appears almost to be 

 divisible into two parts, the anterior half of the muscle being 

 connected with the posterior half by an easily separable fascia ; but as 

 their origins are contiiuious, as well as their insertions, the muscle 

 could in no way be properly described as having two heads. 



HoifmanD, who calls this muscle the m. supracoracoideus, in- 

 forms us in his synonymy that it is the subclavius of Rolleston, the 



