38 
ORCHESTIIDiE. 
AMPHIPODA. ORCHESTIIDjE. 
SALTATORIA. 
Genus— ALLORCHESTES, Dana. 
Dana, United States’ Expl. Exped. p. 883. Proc. Amer. Acad. Arts and 
Sci. ii. p. 206. Amer. Jl. Sci. 2nd ser. viii. p. 136. 
Generic character .— Like Orchestia, but the superior antennae 
are longer than the peduncle of the inferior. Maxillipedes un- 
guiculate. Carpus of the second pair of gnathopoda interiorly 
and anteriorly produced. Telson single. 
The superior antennae are at least as long as the 
peduncle of the inferior. The inferior antennae have 
the two basal articulations not so closely incorporated 
with the head as in Orchestia ; they are, moreover, fur- 
nished with a small olfactory denticle. The mandibles 
are without any palpiform appendage. The foot-jaws 
terminate in a sharp point. The two anterior pairs of 
legs have subchelate hands. Coxae of the fifth pair of 
legs shorter than those of the fourth. Caudal appen- 
dages short and robust. 
Dana established this genus for the reception of cer- 
tain species of Amphipods which had been attributed by 
authors to various genera. It more nearly resembles 
Orchestia than any other genus, but is very easily dis- 
tinguished from it by the length of the superior antennae. 
Upon first consideration, it would seem that this slight 
difference could scarcely be of sufficient importance to 
warrant a generic separation. Closer inspection, how- 
ever, shows that it is associated with some important 
changes both in the structure and habits of the animals. 
