FISHES OP LAKE SUPERIOR. 313 



striated at its surface. The anus is situated a little behind the 

 middle of the length. 



There are generally nine spines on the back ; a single instance of 

 eight has occurred from among a hundred individuals submitted to our 

 examination ; none contained ten. A small triangular and very low 

 membrane extends from the inferior third and inner part of each of 

 them, to rejoin the back. These spines, of an average height of a tenth 

 of an inch, are thin and bent somewhat backwards ; the last, which is 

 bent a little more than the others, is always independent of the soft 

 dorsal. This latter is generally composed of ten, sometimes eleven, 

 soft rays, upon a base of about two-fifths of an inch ; all are bifurca- 

 ted, as is the case with the other fins for three-fifths of their length ; 

 at the anterior margin the rays are almost one-fifth of an inch in 

 height, whilst on the posterior margin they are confounded with the 

 line of the back, which gives to this fin the form of a triangle. The 

 anal, which is exactly opposite to it, has somewhat the same form, with 

 a somewhat shorter base, which recedes a little at its anterior margin ; 

 it contains nine rays, and in a few exceptional cases eight ; it is some- 

 what lower than the dorsal. The caudal is rounded, rather concave 

 on its posterior margin ; there are constantly twelve bifurcated 

 rays, (six in each lobe,) and four rudimentary ones at the upper 

 margin, and as many at the lower ; the inner one has twice the 

 length of the three others ; the largest rays are about one-fifth of 

 an inch in length. The bare space of the upper and lower margins 

 of the tail, which separates the caudal from the termination of the 

 dorsal and anal, varies between one-third and two-fifths of an inch. 

 The pectorals are sometimes as much as three-tenths of an inch long ; 

 they are composed of ten nearly equal rays ; their form is oval, 

 narrowed towards the base. The ventrals are, as in most species, 

 reduced to a spinous ray, inserted on the ossa irmominata, with a 

 small membrane from the axilla, at the centre of which a small sim- 

 ple ray is observed. The spinous ray is here very elongated, since 

 it nearly reaches the posterior extremity of the ventral cuirass, 

 against which it leans when at rest. It is about one-sixth of an inch 

 long, slightly curved within, excavated at the inner side of its base, 

 sulcated on its outer surface, thin like those of the back, and with the 



