224 CONTRIBUTIONS TO MARINE BIONOMICS. 
It cannot be said, however, that the real position and affinities of the 
Corystide are yet established. The reason for this uncertainty is 
probably due to the fact that, as will appear further on, the structure 
of these animals is remarkably modified in relation to sand-burrowing 
habits. Some of these adaptive modifications of structure, which re- 
appear in certain other groups of Crustacea, have undoubtedly impressed 
the minds of certain writers with ideas of homology and genetic re- 
lationship between the Corystide and groups having no real affinity 
with that family. The case affords a new illustration of the inadequacy 
of the purely morphographic method, when unchecked by considerations 
of functional adaptation, for the solution of problems of relationship 
and genetic classification. 
II. STRUCTURAL PECULIARITIES. 
The structure of Corystes cassivelaunus is noteworthy on account 
of the following features. The second antenne are greatly elongated— 
as long as, or longer than, the body—and are fringed along their entire 
length by two rows of hairs, one of which runs along the ventral, while 
the other runs along the dorsal border of the antenna. The hairs of 
each row curve inwards towards those of the corresponding row on the 
second antenna of the opposite side. The second antennz shew a 
marked tendency to approximate to one another longitudinally; the 
opposing rows of hairs then interlock, with the resulting formation of a 
median tube, the lateral walls of which are formed by the jointed 
flagella of the antenne, while the dorsal and ventral walls are fenes- 
trated along their whole extent by the interspaces between the inter- 
locking hairs. The organ formed by the apposition of the second 
antenn I shall term the “antennal tube.” 
The long axes of the three stout basal joints of the second antenna 
are disposed at right angles to one another, and bring about a character- 
istic double bend in the basal part of the antenna. The double row of 
hairs found on the flagellum of the antenna is continued backwards 
along these three basal joints. The hairs on the most distal of the 
three joints interlock with those of the corresponding joint of the 
opposite antenna; the hairs on the anterior face of the deflected middle 
joints bend inwards towards the median line along the sides of the 
rostrum, and together with a median triangular tuft of hairs springing 
from the rostrum itself, form the hairy roof of the proximal part of the 
antennal tube. 
The antennal tube opens posteriorly into a rectangular chamber in 
front of the mouth. This “ prostomial chamber,” as it may be termed, 
is roofed by the rostrum in front, the antennal and epistomial sternites 
