III. COTTOIDS OF NORTH AMERICA. 65 



head slender and elongated, the former tapering quite rapidly away towards the 

 tail ; both covered with a smooth skin ; no teeth on the palatine bones ; cleft of the 

 mouth not extending beyond the eye ; preopercular exhibiting four equal, needle- 

 like, and very delicate spines. The first dorsal fin is separated from the second by 

 a considerable space, and is much the lower. The great development of the second 

 dorsal and the very large eyes might become a specific feature if other species were 

 to be discovered hereafter, for which reason we would not mention them as of 

 generic value. The lateral line, the perfectly smooth skin, and the absence of an 

 isthmus may become as many generic characters. 



The structure of the skull of Triglopsis exhibits the remarkable character of 

 having hollow channels, hitherto only known to exist in Scisenoids, and considered 

 as a characteristic of this group. We now find amongst Cottoids a similar struc- 

 ture, but much less developed in Cotti and Acanthocotti, in which we had over- 

 looked it, before we knew the genus Triglopsis. 



This anatomical peculiarity indicates quite a near relationship between Cottoids 

 and Sciamoids. The representatives of the latter family in this country are all 

 marine, but one. 



TRIGLOPSIS THOMPSOWM, GIRAED. 



PLATE II. Figs. 9 and 10. 

 Syn. Triijlopsis Thompsonii, GIRARD, Proc. Bost. Soc. Nat. Hist. IV., 1851, p. 19. 



It will be easy to form a correct idea of the general form of this species by the 

 accompanying figures, which, although a restoration from several incomplete indi- 

 viduals, we are confident represent its specific features. 



The head is elongated, tapering towards the snout, as the body tapers towards 

 the tail. It forms more than the third, and not quite the fourth of the entire 

 length. Its upper surface is smooth, gradually sloping towards the snout. Its 

 greatest depth is contained twice in its length ; whilst its greatest width forms only 

 the two-thirds of the latter dimension. The snout is elongated, and thus the 

 mouth, which does not extend beyond the entire pupil, is more deeply cleft than in 

 Cotti. The lower jaw is slightly longer than the upper. The teeth are very 

 minute, proportionally more so than in Cotti. They do not exist on the palatines, 

 but the vomer, besides the crescentic band in front, is provided with a narrow strip 

 of similar teeth along the middle line of the posterior branch of that bone. The 

 eyes are very large and elliptical; their longitudinal diameter is contained four 

 times in the length of the head, the same proportion as in many Cotti, but here the 

 head is much more elongated, and accounts for the proportionally greater size of these 

 organs in Triglopsis. The anterior nostrils are nearer the orbit than the snout ; 

 the posterior one is higher up on the frontal line, and still nearer the eye. Both 

 pairs of these openings appear to be tubuliform, but the decomposed state of the 

 specimens did not permit entire satisfaction on that point. The sides of the head 

 are as smooth as the upper surface. The preopercular is the only bone of this 

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