216 OBSERVATIONS ON FISHES. 



common ally, the loach, which, I believe, is more 

 attached to clear running streams with a gravelly 

 bottom. I have kept groundlings alive in a large jar 

 of water for several days, but they remained wholly 

 at the bottom, in the mud I had introduced into the 

 jar, and seldom or never quitted it, except under the 

 influence of alarm, when they would suddenly dart 

 about for a few moments, and then return to their 

 former place of shelter. The small forked spine 

 immediately beneath the eye in this species, easily 

 felt by the finger when passed from below in an up- 

 ward direction, if not readily seen, at once character- 

 izes it; the body is also much more compressed, 

 and the barbules shorter, than in the loach, the only 

 other species with which it can be confounded.* 



* There appear to be two well-marked varieties of the ground- 

 ling, (if they be not distinct species,) which have hitherto been 

 undistinguished by ichthyologists. The difference between them 

 is as follows : 



(1.) One, which I would denominate the large-headed ground- 

 ling, is thicker both in the head and body (the length of the two 

 specimens compared being the same) than the other : the thick- 

 ness of the head in the region of the gills is equal to that of the 

 body, and both are about two-thirds of the depth : the head is also 

 larger ; with the profile very convex in front of the eyes, whence 

 it falls vertically to the lips ; the snout, consequently, is obtuse, 

 with the mouth at bottom, and the lower surface of the head in 

 nearly the same horizontal line with that of the abdomen : the 

 barbules are rather longer than in the other kind ; the suborbital 

 spine, on the other hand, less developed : the eyes are high in the 

 cheeks, the space between narrow, but not elevated into a ridge. 



(2.) The second, which, for distinction's sake, I call the small- 

 headed groundling, is more compressed than the last, especially 

 about the head, which is narrower than the body, and which 



