1866.] ON THE ANATOMY OF THE CRESTED AGOUTI. 391 



from the inside of the sternum, opposite the cartilage of the first rib, 

 and, continuing forwards (upwards) closely united in part, ultimately 

 separate and have their usual insertions. 



The same in the Hare and Guinea-pig. 



The omo-hyoid is wanting. 



The levator claviculee is very remarkable in having an origin by 

 tendon from the basis cranii, immediately to the inner side of the 

 auditory bullae and directly behind the tendon of the anomalous sca- 

 lenus anticus. It is inserted into the clavicle, towards its outer end, 

 immediately opposite the origin of the fourth part of the pectoralis 

 major. 



On the right side we found this muscle closely adherent to the 

 cleido-mastoid above ; but near the clavicle the external jugular 

 vein and carotid artery separated them, after which the two muscles 

 proceeded side by side to the somewhat rudimentary clavicle, the 

 levator claviculee being iuserted outermost. 



On the left side we found no such union with the cleido-mastoid 

 above ; but instead the muscle divided (at the anterior third of the 

 distance between the atlas and clavicle), its broader portion, partly 

 adherent to the trapezius, passing over the shoulder-joint onwards as 

 far as the proximal end of the forearm, simulating a cephalo- 

 humeral (figs. 2 & 3, L. e). But we believe it cannot be a cephalo- 

 humeral, because there is a distinct cleido-mastoid, as before described, 

 entirely distinct and superficial to this abnormally enlarged portion 

 of the levator claviculee. 



It is this portion which evidently has led Meckel* to consider 

 this muscle to be represented by the anterior part of the trapezius 

 in the Agouti. 



Prof. Owenf makes mention of the levator claviculee being pre- 

 sent in two specimens of the Dasyprocta acuschy (111.) dissected by 

 him. 



We ourselves noted its existence in the Guinea-pig, Hare, and 

 Rabbit, — in the former being inserted into the metacromion process 

 of the scapula ; in the two latter it is carried, along with the trape- 

 zius, over the shoulder-joint, fibres passing to the upper part of the 

 humerus. 



In the Hare the levator claviculee is like that which we found on 

 the left side of Dasyprocta cristata, but without the long descend- 

 ing portion to the forearm, rather stopping short at the metacromion 

 process. 



The rectus capitis anticus major is but indistinctly separated from 

 the longus colli, unless what we have called the scalenus anticus 

 should in reality be this muscle, the insertion % of which, however, 

 it must be remembered, is into the first rib, therefore entirely different 

 from that of the rectus capitis anticus major as it ordinarily exists 

 in man. Should our interpretation be correct, the muscle in ques- 



* Op. tit. vol. vi. p. 239. t P. Z. S. 1830-31, p. 76. 



\ Speaking generally, the insertion is oftener to be relied on as indicative of 

 homology than the origin of a muscle — although, perhaps, this rule is more 

 strictly applicable to the limbs than elsewhere. 



