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 musele gréle 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 supracarinales, 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-hemalarches. 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 
