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, 

 u 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. 



