NEBAL1AD.E. 35 



The thorax is divided into eight slender segments, 

 completely concealed within the carapace ; and the abdo- 

 men consists also of eight rings, but which are consider- 

 ably longer and narrower than the preceding. The first 

 four of these are concealed by the carapace, and the other 

 four project beyond it. To the first four we find attached 

 the natatory feet (t. II, f. 1 c], consisting of four pairs. 

 These project from beyond the carapace at its interior 

 posterior portion, and are composed each of an elongated 

 basilar joint, which gives origin to two rather long, strongly- 

 ciliated branches and a very short, simple one. To the 

 fifth and sixth joints we see attached two pairs of what 

 have been described as rudimentary members, and which 

 resemble very much the fulcra or supporters of the ex- 

 ternal ovaries in the Cyclopidse. The penultimate joint 

 wants these organs, but the last gives off at its extremity 

 two rather long appendages, forming the tail. These 

 caudal laminae are smooth on their edges, and are fur- 

 nished with one long slender filament, and three or four 

 shorter ones, not plumose. 



We know very little with regard to the habits of this 

 genus. Otho Fabricius tells us that it carries its eggs 

 under its thorax during the whole winter; that they 

 begin to hatch in the month of April, and that the young 

 are born in May ; they are very lively, he adds, and ad- 

 here to the mother, who appears then to be half dead. The 

 adult swims in a prone state, using its hinder feet to propel 

 it through the water. They are not very active. Montagu 

 informs us, that when moving in the water the superior 

 antennae are in constant motion as well as the abdominal 

 feet, but that the inferior antennas are usually motionless 

 and brought under the body. They are found, according 

 to Leach, on the south-western and western coasts of 

 England, under stones that lie in the mud, amongst the 

 hollows of the rocks ; and Mr. M' An drew dredged it 

 from a considerable depth amongst the Shetland Isles. 



This family contains only one British genus. 



