A STUDY IN OARCINOLOGY. 61 
animals, the exact course of the anterior inhalant ^respiratory current in the 
Raninidaa mast remain largely a matter of conjecture. Nevertheless I have 
not hesitated to put forward the following interpretation based upon a 
detailed study of anatomical facts in the hope that, whilst mj' conclusions must 
necessarily be subject to revision and correction, naturalists who have oppor- 
tunities of studying the live animals may be so far interested as to devote 
some time and trouble to the elucidation of the workings of their respiratory 
mechanisms. The anatomical characters are mo^t easilj' studied in Notopus 
dorsipes, and it is probable that what is true of this species is also true of 
Ranilia muricata, M. Edw , but as I have only been able to examine a single 
dried example of the latter in the British Museum of Natural History, 
I cannot say anything certain about it. I have stated elsewhere (p. 26) 
that, in my opinion, Ranilia, M. ¥iAvi. = Notop'us, de Haan. In Notopus the 
antenna are more primitive, that is to say, they depart less from the 
Macruran pattern, than in any other Raninidse. The peduncle (figs. 29 & 29a) 
is made up oF five distinct segments of which the proximal is admedian in 
position, small, largely concealed by the sub-antennary lobe of the pterygo- 
stome and bears at its inner angle the' aperture of the excretory gland. The 
second segment is also small and largely concealed by the sub-antennary 
lobe : it lies on the same level as the first and is external to it. The third 
segment is large, sub-quadrangular in outline, its extero-ventral surface 
slightly convex and tuberculated,its intero-dorsal surface smooth and slightly 
concave. Its admedian margin is prominent and curved, forming a pro- 
jection which meets its fellow in the middle line. It bears a conspicuous 
tuft of long forwardly directed setse. Its extero-anterior angle is produced 
into a process which embraces the proximal part of the fourth peduncular 
segment; this process is largely developed in other Raninidae but remains 
small in Notopus. The fourth and fifth segments are fairly long, their 
external and ventral surfaces granular and convex, their admedian surfaces 
smooth and flat or slightly concave. The dorsal and ventral edges of these 
smooth admedian surfaces are fringed with long closely set plumose setse 
which, when the two antennae are approximated, interlock with the corre- 
sponding setse of the antenna of the other side. The antennary flagellum 
comprises twenty-six joints, is relatively longer than in any other Raninidae 
(except Ranilia, M.-Edw. and Cosmonotus) and bears a dorsal and a ventral 
row of strong setae which are directed obliquely inwards so as to interlock 
with those of the opposite side when the antennary flagella are approximated. 
Thus there is formed an antennary water-tube (figs. 1 & 56), shorter indeed 
but otherwise similar to and fully efficient as that of Corystes. Water sucked 
down the antennary tube passes into a shallow chamber lying behind the bases 
of the antennaB, the floor of which is formed by the raeri of the third maxilli- 
peds, its roof by the spoon-shaped expanded anterior ends of the exopods of 
