MALACOSTRACA 351 



five pairs of limbs bear gills on the exopodites, while the sixth 

 forms with the telson a tail fan; and a large, branched "liver". 



The 2nd thoracic limb bears a large, raptorial subchela. The 

 alimentary canalh^s a rather simple proventriculus and a large branched 

 "liver"; the latter and the gonads extend along the large abdomen. 

 In the ?iervous system eight pairs of ganglia are fused as the sub- 

 oesophageal ganglion. The heart is very long (pp. 311, 312). The 

 excretory organs are maxillary glands. The larvae are pelagic and of 

 the same general type as the Zoqea but with a peculiar facies of 

 their own. 



The members of the subclass are all marine, and for the most part 

 live in burrows. 



Squilla (Fig. 255) occurs in British waters. 



Fig. 255. A male Squilla mantis. From Caiman, a.' antennule; a." antenna; 

 p. penis; sc. scale (exopodite) of antenna; thJ, th.^, th.^, first, second, and last 

 thoracic limbs. 



Subclass SYNCARIDA 



Malacostraca without carapace; with eyes stalked, sessile or absent; 

 most of the thoracic limbs provided with exopodites and none of 

 them chelate or subchelate; no oostegites; a tail fan; and simple 

 coeca on the mid gut. 



A small group of freshwater malacostracans with a combination of 

 features which forbids their inclusion in either of the other subclasses. 

 In typical genera, they possess most of the features of the caridoid 

 facies except the carapace ; and the relatively slight differentiation of 

 thorax from abdomen, and the use of the appendages of these tagmata 

 as a single series in swimming, are primitive characters possessed by 

 no other member of the class. 



Anaspides (Figs. 212, 256), from pools at 4000 feet in Tasmania, 

 is a normal member of the group. 



Bathynella, from subterranean waters in Central Europe, small, 

 degenerate, and eyeless, has various limbs reduced or absent and the 

 first thoracic segment free. 



