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Show 1884.] MR. G. E. DOBSON ON CAPROMYS MELANURUS. 237 of the sternum almost as far back as its middle third, and, united 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 Cercolabesprehensilis, Hystrix cristata, Erethizon 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 is not represented. Sterno-hyoid (fig. 1, st.h) and stemo-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 (fig. 1, o.h) is thin, without tendinous intersection ; it has the usual origin and insertion. Levator clavicula and levator scapula (fig 1., l.c, & l.s.).-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. Scapuloclavicular is.-This muscle, first described by Cuvier and Laurillard in Bathyergus maritimus, and subsequently by Wood in Cavia aperaa and in Mus decumanus, 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. Pectus abdominis et sternalis (fig. 2, r-r').-Each muscle arises from the transverse process of the manubrium sterni, and, passing |