124 Mr. W. Omer Cooper on Paragnathia. 
larvee, like those of the Gnathiide, are parasitic on fish, 
chiefly on the small flat fish which are frequently so plentiful 
in somewhat brackish water ; they are most easily identified 
by the shortness of the last abdominal segment and by the 
eight-jointed flagellum of the inferior antenne. 
As there does not appear to be any good modern description 
of this species, I give one below, drawn up from an examina- 
tion of specimens from Christchurch Harbour, together with 
a definition of the genus Paragnathia. 
Genus PARAGNATHIA. 
J. & W. Omer Cooper, Zoologist, (4) xx., January 1916, p. 26. 
Flagellum of inferior antenne eight-joited. Male with 
mandibles and maxillipeds similar to those in Gnathia ; 
maxillipeds absent in female. First pair of pereopods 
(gnathopods) in male consisting of five flattened joints only 
partially covering the oral area; in the female with five 
subequal and similar joints, opercular plate absent. 
Genotype. Anceus halidaii, Bate aud Westwood. 
As in Gnathia, the superior antenne have the peduncle 
three-jointed, the flagellum five-jointed in the male, four- 
jointed in the female and larva. The inferior antenne have 
the peduncle four-jointed ; the eight-jointed flagellum is 
one of the points of resemblance between this genus and 
Huneognathia. 
Paragnathia halidaii (Bate and Westwood). 
(Pl. VI. figs. 1, 2.) 
Anceus halidati, Bate and Westwood, British Sessile-eyed Crustacea, 
ii. 1868, p. 203. 
Gnathia formica (non Anceus formica, Hesse), Norman, Ann. & Mag. 
Nat. Hist. (7) xvi. 1905, p. 86. 
Male. Body somewhat elongated, about five times as long 
as its greatest breadth; head subquadrangular ; eyes well 
developed; anterior part of thorax without areolation, 
divided from the posterior by a fairly deep constriction ; 
fifth thoracic segment (third free segment) clearly separated 
from the following ; abdomen much narrower than thorax, 
sides straight, slightly decreasing in breadth towards the 
telson, terminal segment short, triangular, not reaching 
further than the middle of the uropods, provided with two 
sete at the apex. Superior antenne reaching as far as the 
middle of the flagellum of the inferior, which are about the 
same length as the head ; peduncle of the superior antennz 
