218 CRUSTACEANS. 



of the long aiitennce to the caudal fringe ; these antennae are about an 

 inch and a half in length : the smaller antenute between tliem are forked. 

 Two spherical black eyes, without any sensible peduncle, are seated 

 on the back of the head. 



The large claws are terminated by one-half of a forceps, and a hook 

 opposite to it : the caudal segment terminates in five members, whereof 

 that in the centre tapers nearly to a point ; the others are finely fringed. 

 The natural colour is dark grey, approaching black ; but it is ex- 

 tremely variable, often becoming very pale, and sometimes almost white : 

 the integuments are likewise so thin and transparent as to expose both 

 the form and the colour of the food in the stomach of the animal. 



This is a very lively creature, growing quite tame on short confine- 

 }nent, and alwa3^s approaching the \'isitor of its vessel's side ; it is abso- 

 lutely carnivorous, aU animal substances being acceptable to it. 



The shrimp, while supine, frequently seizes fragments, and preserving 

 the same position, swims away with them, around and around the inte- 

 rior of the vessel, all the time devouring its prey. 



An extraordinary change of colour is concomitant on feeding. 

 The shell is often cast ; but no definite external symptom seems 

 either to announce or to regulate exuviation. The true form of the 

 parts is to be best ascertained from the slough, which includes the long 

 antenntB : or, if there be a fissure in any part of the skin, it is in the 

 membrane of the lowest part of the carapace or body-shell, where con- 

 nected with the next segment. The slough is very pale grey, and 

 appears somewhat gelatinous w^hen raised from the water : in a few days 

 it becomes as white as paper. It is not improbable that this is the season 

 of imbecility, enabling the stronger to devour the weaker, while so im- 

 perfectly protected. Specimens have fed the day before exuviation. 



The occurrence of this incident is extremely irregular. A specimen, 

 some time in my possession, was delineated on June 17th, — Plate LX. 

 fig. 1 : on the morning of July 2d, it cast its shell, and this was repeated 

 on the 31st of the same month. The slough, now separating, is repre- 

 sented Plate LXI. fig. 2. A few days afterwards, the animal leapt out 

 of the water and perished — the ordinary fate of the species. 



