776 MR. ST. GEORGE MIVART ON THE [JunC 27, 



latter by the summit of the brachiahs anticus and by the insertion 

 of the epicoraco-humeral. Externally the pectoralis major is inti- 

 mately connected with the outermost layers of the external oblique, 

 while posteriorly, as Meckel remarks*, it is similarly united with the 

 rectus abdominis, of which, indeed, it has every appearance of being 

 the anterior continuation. 



Costo-coracoid (figs. 7 & 9, C. C). A thin sheet of muscular 

 fibres arises from tlie anterior margin of the first sternal rib, and is 

 inserted into the deep surface of that strong tendon which is described 

 below as in part the origin of tlie internal long head of the triceps. 

 This tendon passes from the posterior end of the inner surface of 

 the sternum (close to the hinder end of the edge by which it articu- 

 lates with the coracoid), upwards to the anterior border of the scapula, 

 between the spinous process projecting from that border and tlie 

 point of attachment of the clavicle, and dividing the anterior (or 

 lower) part of the subscapularis from its posterior portion. 



This muscle answers no doubt to that which, in the Echidna-^, 

 goes from the first rib to the coracoid ; for I have found such a muscle 

 in Alligator luchis, and it is noticed by the Rev. Dr. Haughton in 

 the CrocodileJ under the name "pectoralis secundus" — a term I 

 would readily adopt, but that I am inclined to think that the muscle 

 may be the homologue of either the pectoralis minor or the sub- 

 clavius. Stannius§ speaks of it as the sterno-scapular ; but this 

 name has been applied to a muscle widely different Ij. 



Serratus mayniis and levator anyuli seapulce (figs. 2 & 7, S. My.). 

 Several small sheets of muscle proceed from certain ribs to the jjos- 

 terior margin and inner surface (towards the superior margin) of the 

 scapula. These may perhaps include, besides the true serratus mag- 

 nus, not only the levator aiiyuli scapulce, but also the rhomboideus, 

 though I am inclined to regard the latter muscle as absent in the 

 Iguana, not having succeeded in finding the muscle which Meckel 

 speaks of^ as having the same disposition in that animal as in the 

 Chameleon, though absent in Polychrus marmoratus. 



There appear to be four principal portions of this complex 

 muscle: — 



(1) The largest and most posterior portion arises from the outer 

 surfaces of the last two cervical ribs (i. e. those of the eighth and 

 ninth cervical vertebrae) near their free ends. Each rib gives rise to 

 a distinct muscular layer ; and these layers are inserted, in common, 

 into about the upper half of the posterior (or axillary) border of the 

 scapula (fig. 7, S.My. 1). At the lower end of its insertion it is 

 sliglitlv embraced by fibres of the subscapularis, a few of which arise 

 externally to it. 



* Loc. cit. p. 343. 



t Trans. Linn. Soc. 1866, vol. xxv. p. 382. 



I Scientific papers read before the Royal Irish Academy, and published in its 

 ' Proceedings,' 1866, vol. i. p. 702. 



§ Loc. cit. p. 122. 



II Proc. Zool. Soc. 1865, p. 338, and 1866. p. u'JS and figs. 2 & 3, 8. s. 

 4 Loc. cit. p. 312. 



