134 A HISTORY OF RECENT CEUSTACEA 



pairs of legs, are subdorsal in position and of small size. 

 The pleon folds under the trunk. In the female it has 

 five pairs of appendages, of which the first is rudimentary. 

 This legion is divided into two families, the Dromidse 

 and Homolidas, the characters of which are here accepted 

 as laid down in Professor J. R. Henderson's Report on 

 the Anonmra of the Challenger. 



Family 1 . Dromidce . 



The carapace is subglobular, rarely flattened. The 

 eyes are retractile into well-defined orbits. The first an- 

 tennas fold in special fossettes. The fifth and usually also 

 the fourth pair of legs are short, subdorsal in position, 

 and in general prehensile. The vasa deferentia of the 

 male pass through the bases of the fifth pair of legs and 

 form tubular prolongations. 



The family contains some ten genera, one of which is 

 British. 



The species, Dr. Henderson says, inhabit shallow 

 water and moderate depths. The majority protect the 

 body by an ascidian, a sponge, or by one of the shells of 

 a bivalve mollusc. Milne-Edwards says that of the four- 

 teen pairs of brancnise * the last two spring from the last 

 two segments of the trunk, which in the Brachyura in 

 general never carry any. He regards two little lateral 

 pieces intercalated between the sixth and seventh seg- 

 ments of the pleon in Dromia as rudiments of the appen- 

 dages of the sixth segment, but that may be regarded 

 rather as a pious opinion than an established fact. 



Dromia, Fabricius, 1798, almost monopolised the 

 family until it was subdivided by Stimpson into six 

 genera in 1858, this subdivision being grounded chiefly 

 on the disposition of the sternal sulci in the female. 2 In 



1 Branchije are called pleurobranchife when attached to the pleura 

 or sides of the segment, podobranchite when attached to the first joint 

 of the limb, arthrobranchias when they spring from the interarticular 

 membrane between the segment and the limb. 



- For the structure of these sulci and the correspondence of the ap- 

 pendages on the pleon of the male, see the account in de Haan, Fauna 

 Japonica, Crustacea, p. 105. 



