q/Cyclotliiirus didactylus. 247 



Since this muscle coexists witli an iipwanl prolongation of 

 the rectus alxloniinis, it can scarcely be regarded as a " latc- 

 ralized" slip of tlie rectus, as suggested by Prof. ^lacalister*. 

 It is, moreover, completely separated from the rectus by a 

 muscular stratum composed of the thoracic fibres of origin of 

 the obliquus externus. Cuvier figures the muscle very clearly 

 (pi. 257. fig. 2), but terms it " scalene, portion cxterieure ou 

 inferieure." In his plate of the myology of Myrmocopliaija 

 tamandua (pi. 262), it is represented as passing over the serra- 

 tus magnus, I am inclined to regard this muscle, as evidently 

 did Cuvier, as a downward detachment from the scalenus. 



Mr. Wood describes a similar muscle as occurring in man, 

 imder the name of " supracostal " (Proc. Ro3^ Soc. June LSGo, 

 p. 3, and ^lay 1<SG7, p. o23). A like muscle, too, is recorded 

 and figured as a human abnormality in Virchow's ' Arcliiv,' 

 Nov. 1867 (Taf. 6. fig. 1). 



. The rhomboidei are fused together into one muscle. They 

 arise from the up])er third of the dorsal vertebral region, and 

 are inserted along the whole of the superior (or posterior) costa 

 of the scapula ; covered by the trapezius. I did not find any 

 occipito-scapular slip. 



The trapezius arose from the occiput, from the spines of the 

 cervical vertebrae, and from the vertebral spines in the upper 

 third of the dorsal region. It was inserted along the posterior 

 (superior) edge of the spine of the scapula, and into the distal 

 fourth of the clavicle. Meckel notices (Archiv, p. 8S) the 

 clavicular insertion. 

 ' The acromio-basilar was not present. 



The serratus magnus was Avell developed. It seemed to be 

 made up of three factors : — 



1. The highest, evidently corresponding to the levator sca- 

 pulaj, arose from the two or three lower cervical vertebras, and 

 was inserted into the su})erior angle of the scapula and, for, 

 some little distance, along the superior costa of the bone, being 

 overla])pcd by the liighest fibres of origin of the rhomlxiideus. 



2. liic smallest factor, inserted into the inner face of the 

 scapijla, internal to the division just described, arose from the 

 first rib, just external to tlie insertion of the scalenus anticus, 

 with the outermost fibres of Avhich muscle it ajipears to be in 

 intimate connexion. 



3. The lowest, corresponding to the serratus magnus <:»f 

 anthropotomy, arose from the second to the seventh ribs, in- 

 clusive, external to the rectus abdominis, being overlaj)ped at 

 its origin by the outer border of this muscle. A few fibres, too, 



* "Ou the Mj'ologj' of Bradi/pus tridacdjlus,"' Ann. & Mag. Xat. Hist-. 

 July 1800, p. oo. 



