■ROCK GOBY. 155 



The largest I have seen measured nine inches and a half in 

 length, but from six to eight inches is a more usual size. The 

 head and fore part of the body are thick, but narrower before 

 the eyes; the back broad, but the Avhole more compressed 

 posteriorly; cheeks full. Eyes moderate, high; gape moderate; 

 lips fleshy; teeth sharp; under jaw a little the longest. Dorsal 

 fins two, close together, the first beginning opposite the ventral 

 fins, having six rays, which are simple and flexible, and 

 decrease in length from the first; the second dorsal has fifteen 

 rays, of which the tvv^o last are from one root, the last being 

 bent forward to meet its fellow, (but this arrangement is not 

 constant, and consequently does not afford a distinguishing 

 character.) Anal fin shorter than the second dorsal, with 

 thirteen rays, the first and last united in pairs, and the 

 points of these and of the second dorsal bound down with 

 membrane. Pectorals and tail round; ventrals united into a 

 single fin, with ten fan-shaped rays, which at the root are 

 united by a membrane forming an enclosed cavity. Between 

 the vent and anal fin a free process. The colour varies 

 according to the ground: sometimes an intense black, but 

 much more frequently a greyish brown, mottled with darker 

 brown and yellow; darker on the head and back, and the 

 circular border of the tail. 



On one occasion an example was obtained of about three 

 inches and a half in length, which differed so greatly in 

 appearance from what is usual with the Rock Goby, that I 

 was at first inclined to believe it a distinct species; but further 

 examination has led to a change of opinion in this respect. It 

 appeared as if emaciated, with the head not so high, the body 

 more shallow and compressed, more deep at the root of the 

 tail, and the middle rays of the tail more lengthened. The 

 colour a pale grey, with separate well-marked spots of yellowish 

 brown on the head, body, and fins. A figure of this fish is 

 given on the next page. 



As we have already remarked that there is considerable 

 difficulty in distinguishing some of the species of this genus 

 from others decidedly different, we shall copy from Dr. Gunther's 

 catalogue, as quoted above, some supposed unvarying marks by 

 which each one in doubtful cases may be known: — **In the 

 Rock Goby there are eleven or twelve series of scales between 



