166 M. Hesse on new or rare Crustacea of the French Coasts. 



superior antennse are shortest, and composed of three joints ; 

 the inferior have a large basal joint, and are terminated by a 

 cylindrical filament of five joints. The eyes are situated on 

 small rounded protuberances close to the base of the inferior 

 antennae. 



The body is divided into twelve segments, seven thoracic and 

 five abdominal; and, from the arrangement of the former, the 

 animal is enabled to roll itself up into a ball like the woodlice. 

 Each thoracic segment is furnished with a pair of feet, which 

 are articulated laterally to the epimeric pieces at the base of the 

 incubatory laminae ; each foot is formed of five nearly equal 

 joints, and curved in such a manner that its extremity is di- 

 rected towards the ventral surface. The apical joint, which is 

 larger than the others, is inflated above and flat 'beneath, and 

 on the first two pairs of feet forms a sort of elastic pad ; the 

 apical joints of the other feet are hollow internally and nar 

 rowed at the apex, where there is a small contractile aperture 

 with a raised margin. The anterior half-circumference of this 

 aperture appears to be of a more solid substance, and, furnished 

 with denticulations, may render the organ more efficient in 

 fixation. 



The head, abdomen, and whole lower surface of the female 

 are bright yellow, with the two small lateral protuberances of 

 the head reddish brown ; the incubatory plates are light vinous 

 grey, and the branchial laminse transparent and bright blue. 

 Beneath, the segments and epimeric pieces are bounded by 

 white lines. 



The young, on escaping from the egg, are minute and very 

 active, swimming rapidly by jerks. The head is hemispherical, 

 rounded in front, and as wide as the first thoracic segment in 

 which it is immersed ; this is followed by seven other segments, 

 all of the same size, except the last, which has a small rounded 

 process in the middle. The eyes, situated on the sides of the 

 head, are large and hemispherical ; the abdomen is formed of a 

 single piece, as in the male. 



The mouth, which is proboscidiform and retractile, is placed 

 at the lower extremity of an oval protuberance, which projects 

 in the middle of the first thoracic segment. The superior an- 

 tennae are short, stout, and formed of three joints, the last of 

 which is slender and cylindrical, and truncated at the extremity, 

 and the second bears some strong pointed setse. The inferior 

 antennae are much elongated, and composed of five nearly cylin- 

 drical joints, which diminish in thickness from the second to 

 the apex. 



The legs, as in the adult, are seven on each side, and all 

 formed of five joints, of which the last is the movst developed. 



