ZOOLOGY. 
CCXXIX 
Gammarus Nugax. 
Cancer Nugax, Phipps’ Voyage, t. 12., f. 3. 
Abundant on the shores of the Polar Sea at ebb tide. 
Gammarus Ampulla. 
Cancer Ampulla, Phipps, 1. 12., f. 2. 
Several specimens were taken by the trawl in the Polar Sea and in Davis 
Strait. 
Gammarus Boreus. 
G. caudas dorso spinoso, oculis lunatis, pedibus quatuor anticis chelatis, pari septimo praecedentibus 
longiore. 
Sqiiilla Pulex. Degeer Ins., v. 7, p. 525., t. 33., f. 1. and 2. 
Abundant in pools of water left by the ebb tide on the shores of the Polar 
Sea. This species so much resembles in general appearance others which 
are found in similar situations, that a more detailed description than usual 
is required, for the purpose of discrimination. Individuals vary in size from 
half an inch to an inch and half. Body convex, laterally compressed, of 
seven smooth imbricate segments, prolonged in lateral lobes which increase 
successively in size to the fourth, the fifth, sixth and seventh being longer 
and narrower, detached from the segments, and attached to the thighs ; tail 
of six segments, the three first produced in lobes larger than those of the 
body, and acuminating to a sharp point, directed backwards ; the fourth, 
fifth, and sixth segments are less than the preceding, slightly tricarinate on the 
back, and spinous ; the upper antennae rather the longest, being equal in length 
to the head and four first segments ; both pairs are composed of a three-jointed 
peduncle, terminated by a setaceous me.mber, flexible by annular articula- 
tions ; the third joint of the peduncle of the upper pair, and the first of 
the lower, short, the latter with a small spine at the base ; the last joint 
of the upper antennae is much longer than that of the lower, and has a small 
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