III. COTTOIDS OF NORTH AMERICA. 55 



X. COTTUS GOBIOIDES, GIRARD. =-! 

 PIATE II. Figs. 3 and 4. 



Syn. Cot/us fjobloides, GIRARD, Proc. Amcr. Assoc. Adv. Sc. II., 1850, p. 411 ; and, Proc. Boat. 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. RicJiardsonii, 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- 

 sonii. 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 



