86 GAMMARIDjE. 



lessened in diameter. The eyes are moderately large, 

 somewhat reniform, and of a black colour. The upper 

 antennae are equal in length to the head and first two 

 segments of the body taken together ; the peduncle has 

 the first joint as long as the upper margin of the head, 

 the second and third joints are successively shorter; the 

 flagellum, which consists of six or seven articuli, is 

 shorter than the peduncle, but the secondary appendage 

 is nearly as long, though much more slender, than the 

 peduncle. The lower antennae have the peduncle as 

 long as the upper organs ; the first four joints are very 

 short, but the fifth reaches to the extremity of the 

 upper antennae ; it is of a peculiar shape narrow near 

 the base, it suddenly enlarges, leaving a hollow upon 

 the lower margin, that enables the antennae at this joint 

 to be reflected back upon itself, and thus the organ is 

 carried, close pressed beneath the body of the animal, 

 which is its usual position ; from the widest diameter, 

 which is at the extremity of this hollow or notch, the 

 joint gradually tapers to the apex. The flagellum is 

 very slender and long, reaching much beyond the ex- 

 tremity of the animal. Each articulus of the flagellum 

 is a little longer than broad, and carries upon the upper 

 margin, which is slightly raised near the centre for that 

 purpose, a small membranous vesicle, in form like an 

 inverted shoe, from which resemblance Mr. Stimpson, 

 the naturalist of the United States' Expedition to Japan, 

 has given it the name Calceola. The use of these organ- 

 isms is not known ; Mr. Stimpson has, however, informed 

 us that they are peculiar to the males ; whilst our expe- 

 rience tells us that they are not common to the males of 

 all Amphipoda, nor, in fact, to those of this genus ; 

 neither do they appear to be so common to species which 

 belong to the British seas as to exotic forms. 



