1878.] MR. R. COLLETT ON CERTAIN GOBIOID FISHES. 335 



its point is dentigerous, while otherwise the jaw has no teeth ; 

 the innermost part of this jaw forms a sharp edge, which, as the 

 jaws meet one another, places itself inside the corresponding part 

 of the upper jaw, whilst the point of the lower jaw, as "men- 

 tioned above, is encompassed by the outward-bent intermaxillary 

 bones. The point of the lower jaw is square and broad, and has a 

 remarkable similarity to the jaw of a carnivorous animal. On 

 each side of the square point is found a long and curved canine 

 tooth, and between them a row of, together, eight small and acute 

 teeth of the same construction as those in the intermaxillary bones. 



Snout of mature male of Crystallogobius nittsoni in the breeding-season, 

 strongly magnified. 



The female must be pronounced toothless, as such teeth as can 

 be found are partly irregular and partly perfectly microscopical. 

 In a fresh or soft specimen it is scarcely possible to find even a 

 trace of teeth ; but in a dried specimen a couple of very minute and 

 straight isolated teeth may be seen, with the aid of the microscope, 

 on the middle of the lower jaw 5 these, however, are sometimes en- 

 tirely wanting on one side. In a full-grown female the length of 

 these teeth is about -fa to -^ of a millim. 



The fins — The first dorsal fin, which has two rays, becomes 

 only fully developed in the mature or the nearly full-grown male, 

 but is much shorter in the young (not half-grown) male, and 

 rudimentary in the female. In the males it has strong but not stiff 

 rays, which are placed at comparatively large intervals, and con- 

 siderably sloped backwards, and have the point almost bent down- 

 wards, the membrane, which begins already a little in front of the 

 first, continuing behind the last, and running along the dorsal line 

 towards the beginning of the second dorsal fin ; in some specimens 

 Uneven connects both fins completely. The first ray is a little 

 shorter than the second, the length of which does not much exceed 

 the greatest height of the body. In the young males the rays are 

 shorter, and the membrane between them incomplete. In the female 

 they are shortened to such an extent that they can only be discovered 

 by very minute examination; sometimes only one ray seems to be 

 developed. In the female the length of the rays seems never to 

 exceed the length of the eye, and is generally shorter, sometimes 

 having only the length of the crystalline lens. 



