opis. 165 



Pam. GAMMARIDM. 



Adapted for swimming ; mandibles with a palpus. Body 

 generally compressed. Antennae ending in a flagellum, 

 not like legs. Two posterior caudal appendages sometimes 

 short. Legs long and slender. The antennae assist the 

 Gammari very much in obtaining the minute particles of 

 food which abound in the water. Say* describes a species 

 as striking an object of a proper size, when it comes within 

 a moderate distance of its mouth, into the grasp of the 

 four front feet, the first pair of which seem to be most 

 employed. 



Gen. 62. OPIS, Kroyer. 



First pair of legs armed with claws of great size ; second 

 pair of legs not subcheliform ; upper antennae with an ap- 

 pendage, and thick at the base. 



A species of Opis, said to be 0. typica, has been found 

 in Ireland (Strangford Lough, W. Thompson). This was 

 picked off Algae brought up from a depth of fifteen to 

 twenty-three fathoms, where they grew on soft sandy ground. 



* Journal of the Acad. Nat. Sc. Phil. i. p. 375. 



