PERIOPHTHALMID.E 315 



PERIOPHTHALMIDvE 



The members of this family are separated from the other 

 gobioid fishes by the structure of the ventral fins, the eyes, and 

 the pectoral fins. 



The latter have a long, scaly, and very muscular base, which 

 enables them to use the fins as organs of locomotion on land ; by 

 means of them, together with the aid given by the elongate, 

 slender, muscular body, they can make surprising leaps, and 

 progress with astonishing speed over rough, stony ground as 

 well as on smooth muddy or sandy beaches. 



The ventral fins are more or less united, or entirely separate, 

 with a thick muscular base, enabling them to cling with consid- 

 erable force to perpendicular surfaces. The eyes are very close 

 together, on short thick stalks, by means of which they may be 

 elevated for purposes of observation, or they may be drawn in 

 flush with the head ; the outer eyelid is very well developed. 



The body elongate, laterally compressed to subcylindrical, the 

 head large, broad, and deep, abruptly convex or truncate ante- 

 riorly; the body densely covered with small scales, 50 to more 

 than 100, which extend upon the tip and sides of head, or the 

 scales may be very small or rudimentary; the teeth in the jaws 

 are in one or two rows, conical, fixed; there are three large 

 patches of pharyngeal teeth> partly needlelike, partly coarser, 

 and conical; the dorsal fins are separate, the first fan-shaped, 

 highest anteriorly; the caudal is lanceolate or obliquely rounded 

 and in some genera has the lower margin obliquely truncated; 

 the gill openings are rather narrow, the isthmus broad; bran- 

 chiostegals 5. 



Tropical shore fishes of wide distribution. Some of the spe- 

 cies soon drown if placed in deep water from which they cannot 

 emerge, at least in part. Four genera occur in the Philippines. 



Key to the China Sea genera of Periophthalmidas. 



a 1 . Teeth erect in both jaws. 



b\ Scales small, 75 to 100, first dorsal X-XV, the ventrals divided, merely 



united at base Periophthalmus. 



6 2 . Scales larger, 50 to 60, first dorsal 0-XV, the ventrals nearly com- 

 pletely united in adults, separated in the young Periophthalmodon. 



a 2 . Teeth horizontal in lower jaw, the ventrals united. 



c\ Scales 60 to 100, dorsal V, 1-23 to 27; teeth in lower jaw with dilated 

 tips, truncated or slightly emarginate or lobate.. Boleophthalmus. 



