THE MYOLOGY OF AMIURUS CATUS. 329 



origin from the centrum and processes of each vertebra. Each 

 ■myomere, therefore, corresponds in its position to a primitive ver- 

 tebra. For the purpose of description, the lateral muscle of each side 

 may be divided into five longitudinal parts, not in all cases perfectly- 

 separable, but still sufficiently so for the purpose. 



The first, or most superior portion, is not represented anteriorly, 

 but commencing at the posterior ray of the dorsal fin, it runs back- 

 ward to the rays of the caudal fin. It is the muscle termed by 

 Owen the supracarinalis, and by Cuvier le muscle grele superieur. 

 It consists on either side of a thin band of muscular fibres, formed 

 by the union of slips arising by tendons from the spinous processes 

 as far forward as that of the second vertebra behind the last inter- 

 spinal of the dorsal fin. From their tendinous origins the fibres of 

 each slip run obliquely forwards, the upper fibres being horizontal and 

 continued over to the next myomere. This muscle belongs, as far as 

 its action is concerned, to the dorsal fin, since its function is to depress 

 that structure, but from its origin it is plainly comparable to the 

 series of myomeres of the lateral musculature. 



The second portion is the largest, and is formed of that part of the 

 lateral muscle above the lateral line. Separated from its fellow 

 of the opposite side, posteriorly, by the supracar ingles, it is in con- 

 tact with it anteriorly, and shows no division into myomeres. 

 Posteriorly, however, the segmentation is distinct, especially towards 

 the lower edge, the distinctness vanishing anteriorly more rapidly above 

 than below. The myocommata are bent abruptly so as' to form an 

 angle pointing backwards, and, accordingly, each myomere fits into 

 the succeeding one, a transverse section of the body cutting through 

 several. Anteriorly this portion is inserted into the supraoccipital 

 bone and spine, the exoccipital, epiotic and pterotic. Fibres also 

 pass to the upper surface of the plate formed by the transverse pro- 

 cesses of the 3rd and 4th vertebrae, and some of the more superior 

 ones are fastened to the under surface of the plate of the dorsal fin. 



The third portion lies immediately below the lateral line ; it is 

 not perfectly separable from the second portion, and still less so from 

 the fourth. Its fibres anteriorly run between the transverse processes 

 and ribs, and the myocommata from these, and posteriorly between 

 the myocommata from the haemal arches. In consequence of this the 

 plane of the myomere is curved anteriorly, being horizontal in its upper 

 portion where it is attached to the transverse processes, and vertical 



