336 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
prof. Davidoff! in his valuable papers on the pelvis and pelvic mus- 
culature of fishes, treats the 7'’eleostei very summarily, merely stating 
that the differences in musculature and innervation between the 
Teleosts and Lepidosteus, or, more especially Amia, are quite unim- 
portant. In comparing Amiwrus with his descriptions of either of 
the two forms mentioned, although the ground-plan is much the same 
yet the details are much simpler, it being impossible in Amiurus to 
distinguish, for instance, in the ventral musculature a pars media, or 
in the abd. prof. a caput longum from a caput breve. The names em- 
ployed above for these muscles indicate their equivalency with those 
of the pectoral arch. 
IX.—MUSCLES OF THE DORSAL FIN. 
Owing to the modifications of the anterior rays of the dorsal fin in 
Amiurus, their muscles are also modified. Those of the five posterior 
rays have a typical arrangement. The extrinsic muscles are two in 
number, namely, the anterior superior fibres of the upper portion of 
the lateral musculature, hich pass from the supraoccipital to the 
anterior portion of the plate which supports the defensive ray, and 
will have little or no action in moving the fin, and the swpracarinales 
which will depress the rays. 
Of the intrinsic muscles there are two to each ray, an erector and 
a depressor. The typical arrangement -of these may be seen in the 
posterior five rays. In these each erector lies anterior to the depres- 
sor, and arises from the posterior border of the interspinal of the pre- 
ceding ray. The depressors arise from the anterior border of the in- 
terspinal of the ray to which each belongs, and from the spinous pro- 
cess of the vertebra which supports that ray; each crosses its 
interspinal obliquely above so as to lie behind it. The erector is 
inserted into the anterior and the depressor into the posterior surface 
of the base of each ray. 
Of the muscles of the next anterior ray, ¢.e., the fourth? the de- 
pressor is normal in its relations, arising from the anterior surface of 
the fourth interspinal and the extremity of the spinous process of the 
sixth vertebra, and, crossing over the interspinal, is inserted into the 
1 Davidof—Beitr. zur vergl. Anat. der hinteren Gliedmasse der Fische, ii. Th. Morph. Jahrb. 
vi., 1880. 
2 This will be the third apparent ray, the first having lost all its ray-like appearance. See 
paper on Osteology. 
