122 Mr. W. Omer Cooper on Paragnathia. 
leneth about one-fourth the width of the arm, overlapping 
slightly the base of the succeeding upper arm-plate ; beyond 
the seventh the upper arm-plates are separated for an 
increasingly large distance by the dorsal apposition of the 
side arm-plates. 
The side arm-plates are very large, with the dorso-lateral 
border forming a sharp keel which is produced into a thin 
knife-like border, increasing in height distally. 
Within the sharp point formed by the outer corner of the 
side arm-plates is a single, flattened, very thin spine, about 
half as long as the segment, at first leaf-like, soon becoming 
triangular, which is closely appressed to the arm and over- 
laps the proximal part of the succeeding side arm-plate ; 
viewed from below this spine forms a perfect continuation 
of the lateral production of the side arm-plate. 
The first under arm-plate is a slightly shortened pentagon 
with strongly concave sides and sharply rounded corners ; 
the next is six-sided, elongate, the lateral edges strongly 
concave, the proximal angle truncated by the first, the distal 
angle overlapping the base of the third, the proximal and 
distal borders concave ; the following rapidly decrease in 
size, becoming smaller and separated from each other by the 
apposition of the side arm-plates. 
There are two strongly curved tentacle-scales forming 
between them a funnel enveloping the base of the tentacle. 
The first arm-tentacle lies just beyond the distal end of 
the mouth-frames, between the side mouth-shields and the 
first under arm-plate. 
Type. Cat. no. 388584, U.S.N.M., from ‘ Albatross ” 
Station 2818, among the Galapagos Islands, in 392 fathoms. 
XVI.—On Paragnathia, a Genus of the Crustacean Family 
Gnathiide. By W. Omer Cooper, F.L.S. 
[Plate VI.] 
In the course of collecting along the shores of Christchurch 
Harbour, Hants, in May 1915, I came across a number of 
colonies of Gnathiidee, consisting principally of specimens 
in the late Praniza stage and of a brilliant green or yellow 
colour, They were at first taken to be Gnathia mazillaris 
(Mont.), but upon a more careful examination it became 
apparent that they belonged to the species described by 
Bate aud Westwood under the name of Anceus halidaii, and 
