Il. COTTOIDS OF NORTH AMERICA. 
On 
Or 
X. COETUS GOBRBIOIDES, Girarp. 
Prare II. Figs. 3 and 4. 
Syn. Coltus gobioides, GIRARD, Proc. Amer. Assoc. Ady. Se. II., 1850, p. 411; and, Proc. Bost. Soc. Nat. 
Hist. III., 1850, p. 189. 
The first impression which strikes the observer after a superficial glance at this 
species, is a general resemblance with C. Richardsonii, from which it differs, how- 
ever, much more than from several others, by several peculiarities of its structure. 
What leads to this impression is its large mouth, its large head, and undoubtedly 
its profile, as well as the general outline of the body. But as these species belong 
to two different sections, their intimate affinities are found more remote than might 
be anticipated. 
Its large mouth distinguishes it readily from all the species, which possess, like 
it, three soft rays only to the ventral fins, with the exception, perhaps, of the fol- 
lowing species, to which it has much affinity. 
The greatest depth of the body is contained five times and a half in the entire 
length from the snout to the tip of the caudal fin; whilst the least depth enters 
in it nearly fifteen times. These dimensions, when compared to those in C. bole- 
oides, are very striking, when we bear in mind the absolute size of the individuals 
which we here describe. In C. boleoides, three-quarters of an inch shorter than C. 
gobioides, we find both the greatest and least depth comprised a greater number of 
times in the length. The greatest thickness is a little less than the depth on the 
anterior region. 
The head forms three-eighths of the entire length, proportionally a little shorter 
than in C. boleoides. Besides, it is much broader than deep, and its frontal length 
is sensibly equal to its width. The flattening of the head above the eyes and the 
convexity of the neck, make the frontal line appear’ as if more depressed than in 
other species. The snout is obtuse, differing greatly in this respect from C. Richard- 
soni. The angles of the mouth reach a vertical, which would pass beyond the 
pupil. The eyes themselves are circular and proportionally small; and_ their 
diameter is contained a little more than four times in the length of the head. The 
interorbito-frontal space is greater than in C. boleoides. The preopercular spine is 
much developed and stout, suddenly curved upwards. The spine of the suboper- 
cular is small and acute. The gill openings are large and oblique, and separated 
under the throat by an isthmus of four-eighths of an inch. 
The first dorsal commences one inch and one-sixteenth from the extremity of 
the snout, and extends on a basis of half an inch, leaving a considerable space to 
be filled by the membrane. The origin of the second dorsal is opposite to the vent, 
and composed of seventeen undivided rays. Its upper edge is more convex than 
in C. boleoides, the first and last rays being sensibly shorter than the middle ones. 
The commencement of the anal takes place between the third and fourth rays of 
the second dorsal; it is higher than the latter, and composed of twelve undivided 
rays. The caudal is rather rounded than truncated posteriorly, and is contained but 
a little less than six times in the entire length. Its eight middle rays are bifurcated 
