1884.] MR. G. E. DOBSON ON CAPROMYS MELANURUS. 237 



of the sternum almost as far back as its mirldle third, and, nnited by 

 their contiguous internal margins, pass forwards, overlying part of 

 the origins of the great pectoral muscles, and, concealing the sterno- 

 mastoid and other muscles arising from the extremity of the sternum, 

 are inserted into the rami and angles of the mandible. 



These muscles are much more developed than usual in Rodents, 

 resembling rather the corresponding structures in certain species of 

 Insectivores, as in the Hedgehogs, in Gymnura raffiesii, &c. ; in 

 Gercolabes prehensilis, Hystrix cristata, JErethizon dorsatus, Octodon 

 cumingii, and other species of hystricine Rodents examined by the 

 writer they were found slender, scarcely exceeding the sterno- mastoid 

 in lateral width. 



Sterno-maxillaris h not represented. Sterno-hyoid (fig. ], st./i) 

 and sterno-thyroid muscles present no peculiarities. 



Sterno-mastoid (fig. 1, st.m). — Arises from the extremity of the 

 sternum and from the sterno-clavicular articulation, under cover 

 of the preceding muscle, and is inserted with the cleido-mastoid into 

 the mastoid process. 



Cleido-mastoid (fig. 1, cl.m). — Arises from the commencement 

 of the middle third of the clavicle, and is inserted into the mastoid 

 process with and behind the preceding muscle. 



Cleido-occipitalis is united with the trapezius (see further on). 



Digastric. — These muscles are quite separate ; each arises from 

 the large styloid process of the temporal bone, and is inserted into 

 the commencement of the short horizontal ramus of the mandible in 

 front of the union of the coronoid process. There is no trace of 

 tendinous intersection, but the surface of the muscle towards its 

 anterior half is tendinous. 



Omo-hyoid {f\g. 1, o.h) is thin, without tendinous intersection ; it 

 has the usual origin and insertion. 



Levator claviculce and levator scapula; (fig 1., l.c, & /.«,). — Arise 

 together from the basis cranii but soon separate, the former becoming 

 attached to the outer third of the clavicle, the latter to the acromion, 

 both overlying the attachments of the united trapezius and cleido- 

 occipital muscles. 



Subclavius (fig. 1, s.c) is well developed, arising from the cartilage 

 of the first rib and costo-sternal articulation, and is inserted into the 

 outer third of the clavicle. 



Scapulo-clavicularis. — This muscle, first described by Cuvier and 

 Lanrillard in Bathyergus 7naritimus, and subsequently by Wood in 

 Cavia apercea and in Mus decumanits, is well developed. It consists 

 of a broad flat muscular aponeurosis, which extends from the outer 

 two thirds of the upper margin of the clavicle (where it appears to 

 be continuous internally with the origin of the cleido-mastoid), to 

 the anterior margin of the spine of the scapula and vertebral margin 

 of the pre-scapula, lying on the supra-spinatus and omo-hyoid 

 muscles, and covered superficially by the united trapezius and cleido- 

 occipital. 



Rectus abdominis et sternalis (fig. 2, r-r'). — Each muscle arises 

 from the transverse process of the manubrium sterni, and, passing 



