EOCK GOBY. 
155 
The largest I have seen measured nine inches and a half in 
length, hut 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 hack broad, but the whole 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 two last are from one root, the last being 
bent forward to meet its fellow, (but this arrangement is not 
constant, and consequently does not alFord 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 dilfered 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 
i 
