ccxxx 
APPENDIX. 
seta at the base. Head rounded, obtuse, without a rostrum ; eyes black, 
lunate, at the base of the upper antennae ; legs fourteen ; the two first pair 
with a strong compressed hand, monodactyle ; the hand of the second pair 
broadest ; third and fourth pairs, alike and similar in size, directed forward, 
slim, and compressed, five -articulate (the second joint being very short), 
and ending in a curved nail ; similar to these are the fifth, sixth, and seventh 
pairs, but directed backwards, the nails curving forward ; these three last 
pairs are unequal in size, increasing successively from the fifth to the 
seventh, the sixth pair being considerably the smallest. The less are setose, 
especially at the joints. Swimmers three pair, being each a fleshy pe- 
duncle, with two plume-shaped branchial terminations ; the fourth and 
fifth caudal segments are furnished with a pair of lateral bifurcate style 
processes, the outer style of the second pair being shorter than the inner ; 
the sixth caudal segment terminates in a pair of small lanceolate plates, 
bristled at the apex, beneath which are inserted two peduncles, each bifur- 
cating into oblong, stiff, and narrow plates, the outer of which are larger 
than the inner ; colour usually pale, with a small red spot on each of the 
lateral lobes of the three first caudal segments. This description applies 
strictly to the many specimens which have passed under examination. 
The Squilla Pulex figured by Degeer, /. c., differing in no respect from the 
above description, is considered to have been an individual of the same 
species, and it is therefore believed to be common to the northern 
shores of Europe and America ; the Squilla Pulex has been considered a 
synonym of the Gammarus Pulex of modern authors, but erroneously, 
as may be seen by comparing the figure in Degeer with that of the Gam- 
marellus Pulex, Herbst., vol. ii., 130, tab. 36, fig. 4 and 5, which is the Gammarus 
Pulex of J. C. Fabricius, Ent. S^st., and of Latreille, Enc^cl. Meth. pi. 328, 
fig. 11-15; the species are very distinct, differing in the lateral lobes, 
in the mucronate production of the caudal segments, in the absence of the 
carinae and spines on the three posterior segments of the latter, and in the 
shape of the eyes : the Gammarus Pulex of Montagu, Linn. Tr. ix, t. 4, f. 2, 
