330 



CUM AD ;E. 



rostrum is sharp-pointed, and Lent considerably upwards ; the eyes are small, 

 and the dorsal ridge immediately behind the eye is surmounted with three 

 thick short spines. The second thoracic segment is of considerable extent at 

 its dorsal part, but is quite obsolete at the middle ; it again, however, makes 

 its appearance at its inferior part, where it supports the second pair of com- 

 pound legs. The four following segments gradually decrease in size : the 

 superior antennae are of considerable size, oblong and spinous. The inferior 

 antennae are much longer than the rostrum. The ambulatory division of the 

 first pair of legs is extremely short, and the first joint is of no great breadth. 

 The natatory division it about the same length as the first joint of the anterior 

 division. 



The second pair of legs are very long and slender ; the first segment is not broader 

 than the following joints, and is armed internally at its extremity with a very 

 long spine. 



The simple feet are extremely spiny. 



The abdominal portion of the body is very long and slender, the fifth segment be- 

 ing the longest. The caudal styles are long, slender, and pointed ; the internal 

 scale has the last joint pointed and armed with two spines ; the last segment 

 of the external scale is more obtuse. 



Genus ALAUNA, mihi. 



Generic Characters. The superior antennae are composed of a peduncle and a 

 multiarticulate filament. The inferior antennae are eight-jointed. The first 

 three pair of legs are compound. The internal scale of the caudal style is com- 

 posed of three segments, and the external of one. 



Alauna rostrata, mihi. 



Description. The whole animal is of a beautiful bright straw colour, inclining to 

 yellow. The thoracic portion of the body is very large and swollen. The 

 first segment or carapace is almost oval. The rostrum is long, pointed, and is 

 bent upwards at its extremity. The eyes, which are of considerable size, are 

 situated at the base of the rostrum. The superior pair of antenna? are very 

 slender, consisting of a delicate filament covered with hairs, which arises from 

 a short peduncle ; these antennae are almost equal in length to the rostrum. 



The inferior antennae are much longer, consisting of eight joints slightly spinous ; 

 the distal extremity of the third is armed with a strong multiarticulate spine. 

 The footjaws are seen projecting considerably beyond the edge of the carapace ; 

 they are very spiny, and the last joint but one is armed with a long articulated 

 spiniferous spine. 



The first pair of legs are extremely short ; the thumb-like process at the extre- 

 inity of the ambulatory division is single-jointed and spiniferous. The second 

 pair of legs are also short. The ambulatory division of the third pair of legs is 

 very long and slender, being almost as long as that of the second pair of legs ; 

 the fifth joint is the longest. The natatory division is as long as the first four 

 joints of the ambulatory. The simple legs are very spiny on their anterior 

 edges. 



