90 
GAMMAR1M1. 
AMPHIPODA. L YSIA N A SSI DBS. 
NAT ATOM A. 
G-enus — ANONYX, Kroyer. 
Anonyx Kroyer. Gronland, Amfip. p. 15 ; Nat. Tidsk. v. ii. p. 256. 
Generic character . — Superior antennae short, pyriform, furnished 
with a secondary appendage. Mandibles having a smooth 
incisive margin and a palpiform appendage. First pair of 
gnathopoda subchelate ; second pair long, slender, feeble, and 
subchelate. Telson single, squamiform, cleft. 
This genus was separated from Lysianassa by Kroyer, 
from the subchelate form of the hands of the third 
pair of limbs (“ parvulo instructi ungue ”), and from the 
fourth pair of limbs being destitute of a terminal hook, 
(whence the generic name,) the place of which is sup- 
plied by a brush of hairs. Also the middle tail-piece, 
instead of being entire, as in Lysianassa , is divided more 
or less deeply in Anonyx. Neither of these characters 
are capable of being distinguished without close exami- 
nation, and in some species, Anonyx lagena for example, 
the extremely oblique palm of the hand approximates, 
in its form, to that of a Lysianassa ; again, the divi- 
sion of the central tail-piece is occasionally so slight, 
as in A. obesa , that a small depression alone exists. 
The genus Opts, of which Kroyer has described two 
species, differs from Anonyx in the opposite extreme. 
As Lysianassa has a less perfectly chelate hand than 
Anonyx , so Opis possesses one that is still more perfect 
as a didactyle claw. 
This grouping, although convenient, appears to us to 
be arbitrary ; moreover, it is not improbable that some 
of the forms may be only sexual. 
