1881.] ANATOMY OF THi; ERINACEID^. 39>'5 



continued forwards between the rami of the mandible, concealing 

 the greater part of the mylo-hyoid muscles (which are very thin, 

 and do not extend beyond the middle of the interniandibular si)ace), 

 and are inserted laterally (under cover of and united at their insertion 

 with the superficial laminae, but extending anteriorly for a short 

 distance beyond them) into the sides of the jaws. 



This peculiar development of the digastric has been described as 

 an anomaly in man, but is known as a normal condition in Chiromys 

 madayascariensis and in some other Primates '. The writer has 

 found it well marked in certain species of Chiropteia, as in Epomo- 

 phorus macrocephalus and E. minor, where, although the united 

 internal lamina? of the muscles extend as far backwards as to cover 

 the hyoid bone, there is no connexion with it. It is especially 

 noticeable in this case that the tendinous intersection is vertical, or 

 nearly so, corresponding to the position of the posterior margin of 

 the united muscles, as the oblique intersection in O. rafflesii corre- 

 sponds to the more anterior position of the posterior margin of the 

 same muscles in the latter species ; and we may reasonably conclude 

 that the tendinous intersection of the digastric, wherever met with 

 in Mammalia — whether as a true tendon, as in the Primates, or as a 

 mere tendinous inscription, as in many species of Chiroptera and of 

 Insectivora — has primarily originated as the origin of a tendinous 

 posterior raphe, such as we find in Gijmmira rafflesii ^. 



The sterno-mastoicls and cleido-mastoids are large, and, except at 

 their insertions, separate ; the deido-occipital is united for a con- 

 siderable distance with the trapezius, and really appears to be part 

 of that muscle inserted into the clavicle. The omo-hyoid is well 

 developed, and has the usual origin and insertion. Levator scapuke, 

 from the transverse process and anterior arch of the atlas, is inserted 

 into the extremity of the outer bifurcation of the acromion, super- 

 ficial to the insertion of the trapezius, to the surface of which its 

 posterior and upper margin is attached. The trapezius is double. 

 Its occipital and cervical portion is well develo))ed, arising from the 

 inner three fourths of the occipital crest, from the centre line of the 

 neck, and from one or two dorsal spines. Some of the anterior fibres 

 separate about the middle of the neck to form the c/ezrfo-occipital 

 (or is the cleido-occipital united at this point with the trapeziiisl) ; 

 the remaining fibres are inserted into the spine of the scapula from 

 the acromion to its posterior root. The posterior trapezius arises 

 from the last five or six dorsal vertebrae, and is inserted into the 

 posterior third of the spine of the scapula. 



The rhomboideus anticus has the same origin as the trapezius, with 

 the addition of three or four dorsal spines ; it is folded at its in- 

 sertion into the posterior margin of the scapula. Rhomboideus 

 posticus is a small flat muscle, which passes from the sj)ines of the 

 fourth, fifth, and sixth dorsal vertebroe to the internal surface of tlie 

 middle of the posterior margin of the scapula beneath the /•. major. 



' Owen, Comp. Anat. iii. p. 53. 



- On tliis subject see my ));ipcr " On the Tomlinous luterseelion of Ibe 

 Digastric," Proc. Koy. Soc. M;ircli ol, 1881. 



Proc. ZooL. Soc— 1H81, No. XXVI. 26 



