Dr John Anderson on Phryxus paguri. 377 
upon its ventral surface four rounded tubercles, and has a 
curious crescent-shaped pedunculated appendage attached 
to the posterior extremity of its external margin ; the pos- 
terior portion is about half the size of the anterior, and 
is convex externally, and slightly concave on its internal 
margin. 
The connections of the remaining five pouch-like mem- 
branes are as follows :— 
The 2d belongs to the 1st Thoracic segment. 
„ 3d ,, „ 2d . do. 
„ 4th „ „ 3d and 4th do. 
„ 5th „ „ 5th and 4th do. 
„ 6th „ „ 5th, 6th, and 7th do. 
The second membrane covers the valve-like leaf of the head 
and is overlapped by the third, which is partially covered by 
the fourth ; this, again, overlaps the anterior extremity of 
the fifth, the remainder of which, and the posterior half of 
the fourth, are hidden from view by the largely developed 
pouch of the fifth, sixth, and seventh segments. By this 
arrangement the plates visible from the belly side are the 
third, fourth, and sixth. The sixth plate is minutely serrated 
along its margins. In one of the specimens I examined, 
the fourth, fifth, and sixth membranes were filled with ova. 
The pale-yellow coloured male is a very little more than 
one line in length, and consists in all of nine segments, 
which diminish in size as they approach the caudal extre- 
mity. The anterior segment (head) is symmetrical, and 
bears two eyes. Projecting beyond its lateral margins are 
the external antennae, which consist of four joints. Placed 
internal to these, and completely concealed by the head, 
are the internal ones, which only consist of three joints. 
Each of the remaining segments, with the exception of 
the terminal one, carries a pair of feet which are provided 
with sharp claws. The segments are rounded at their ex- 
ternal margins. 
