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Show 28 DR. Y. O. PARSONS ON T H E [Jan. 15, Trunk-Muscles. Panniculus carnosus.-This is very specialized, probably in connection with the underground habits of the animal, so that the typical mammalian dorso- aud abdomino-humerahs muscles are remarkable for their absence, and their characteristic relation to the pectoral muscles is wanting. As usual, there are many layers of fibres in the panniculus, and to many of these special names have been given by Dobson. The main scheme consists of a longitudinal set of fibres running over the back region from the root of the snout to the root of the tail, forming Dobson's occipito-frontalis and dorso-cuticularis, while various oblique bands cross the general antero-posterior direction of the fibres and acquire attachments to fixed points, such as the acromion process, the elongated auditory meatus, and the ligamentum nuchas. In this way the acromio-cuticularis, occipito-euticularis, dorso-cuticularis, cervico-cuticularis, cervico-auricularis, and retractor naris are formed ; muscles which in our specimen fully bore out Dobson's descriptions of them (text-fig. 6, p. 27). The ventral panniculus consists of the platysma in the neck and a set of abdominal fibres which have the same direction as those of the external oblique; some of these fibres are prolonged down over the anterior (cephalic) surface of the leg as far a3 the dorsum of the foot. There is, so far as I could see, no indication of the sterno-facialis or sphincter colli so common among mammals ; but a muscle runs almost directly outward from the manubrium sterni on a deeper plane than the ventral panniculus with u Inch it ultimately blends, and is well-named by Dobson the sterno-cuticularis. The specimen in my possession shows that this muscle lies superficial to and probably compresses the anterior of the two mammary glands. The posterior mammary gland lies in the groin and extends as far as the front of the knee, it is merely covered by the general fibres of the ventral panniculus. The muscles of the head, neck, and trunk closely correspond with Dobson's descriptions ; perhaps the following points, however, may be worth calling attention to. There are three separate parts to the sterno-cleido-mastoid : - 1 . The sterno-mastoid is inserted separately by tendon. 2. The cleido-mastoid is inserted by flesh. 3. The cleido-occipital which near the clavicle lies superficial to the last, and is separated from it by the spinal accessory nerve. The two parts of the trapezius are widely separate as in Dobson's specimens ; the anterior portion only is inserted into the acromion. Both parts are supplied by the spinal accessory nerve. The hinder (caudal) part of the rhomboids passes across the mid-dorsal line to join its fellow of the opposite side. This arrangement is described by Dobson as the transversus scapularum, and reminds one of a similar arrangement of the acromial fibres of the trapezius (acromio-cucullaris) described by Prof. Windle and mvself in certain Carnivores l. 1 ,: Myology of the Terrestrial Carnivora," P. Z. S. 1897, p. 385. |