156 THE CRUSTACEA 



podite is defined from the basipodite, at least in the last pair, 

 and Hansen recognises a minute terminal segment as well as a 

 pre-coxal, making altogether nine segments in the axis of the limb. 

 In Nebaliopsis the thoracic limbs are very different from those of 

 the other genera. Except the first and last pairs, they are unseg- 

 mented lanceolate lamellae (Fig. 90, D), having a slight lobe on 

 the outer edge to represent the exopodite, and a more distinctly 

 marked bilobed epipodite ; the inner edge is beset with setae 

 along its whole length. In the last pair, which are almost without 

 setae, a terminal segment is marked off, and in the first pair 

 (Fig. 90, C) this part, although not distinctly segmented off, is 

 produced into a finger-shaped distal lobe (en). 



In Nebalia the tip of each of the thoracic limbs carries, in the 

 breeding female, a fan of long plumose setae turned inwards to 

 form the floor of a basket -like brood -chamber which is closed 

 behind by rows of long setae on the inner edges of the last pair. 



The first four pairs of abdominal appendages are biramous and 

 are used in swimming ; the last two pairs are small and uniramous. 

 The former (Fig. 91) have a stout protopodite of two segments and 

 long indistinctly segmented rami fringed with spines and plumose 

 setae. From the inner edge of the endopodite close to its base 

 there springs a short appendir, internet (a.i) bearing a group of 

 hooked spines at its tip. 



Alimentary System. The masticatory stomach, in Nebalia, is of 

 a comparatively simple type. It is divided into a " cardiac " and a 

 " pyloric " portion, the former with masticatory ridges moved by 

 muscles, and the latter with two pairs of lateral setose lobes and a 

 dorsal groove which is continued as a delicate chitinous funnel, 

 open below, some distance into the mid-gut. The mid-gut extends 

 back to the penultimate segment of the body. Four pairs of 

 hepatic caeca open near its anterior end and a pair of short caeca 

 open separately on the ventral side in the same region. Near its 

 junction with the proctodaeum the mid-gut gives off an unpaired 

 dorsal caecum, bifid at the tip. 



Circulatory System. The heart, in Nebalia, extends from the 

 cephalic region to the fourth abdominal somite. It has seven pairs 

 of ostia, and the last pair, which are larger than the others, are 

 situated in the region of the sixth thoracic somite. The exopodites 

 and epipodites of the thoracic limbs are traversed by a close net- 

 work of blood-channels and no doubt serve as respiratory organs. 

 The valves of the carapace probably also assist in respiration, and 

 the blood circulating in them is returned to the pericardial sinus by 

 a definite venous channel on each side. 



Excretwy System. Both the antennal and the maxillary glands 

 are present in a vestigial condition, the former lying in the 

 proximal segment of the antennal peduncle, while the latter is 



