72 A HISTORY OF RECENT CRUSTACEA 
and five-jomted. Mr. Miers says, ‘The nearest ally to 
Acanthocyclus is, I think, Bellia {Milne-Edwards, 1860], 
which resembles Acanthocyclus in the more or less orbicu- 
late carapace, in the form of the front, chelipedes, and 
ambulatory legs, but is distinguished by the narrower, 
more elongated merus [fourth joint] of the exterior maxil- 
lipedes, by the broader post-abdomen [pleon] of the male, 
and the less distinctly defined buccal cavity.’ 
The legion Cyclinea, which cannot boast with certainty 
of more than a single genus and single species, may 
hope to have its ranks filled up in the course of time. At 
present it does not make a very good show, even on 
paper. 
Legion 3.—Corystinea. 
The second antennez have elongate flagella. The 
third maxillipeds usually do not make a complete closure 
of the mouth-cavity and are extended over the anterior 
margin of its frame. The sternal plastron is narrow. The 
single family Corystidee does not require a separate defini- 
tion. It does not appear to contain more than eight genera, 
three of which are included in the fauna of Great Britain. 
Corystes, Latreille, 1803, has a very distinguishing charac- 
ter as compared with the forms previously discussed, in 
that the carapace is not transverse, but much longer than 
it is broad. Corystes cassivelaunus (Pennant) has fre- 
quently attracted attention by the amusing resemblance of 
the carapace to a human countenance, which Herbst com- 
pares to the broad-nosed Kalmuck type. It is in Great 
Britain a convenient species for study, from the number of 
dead specimens that are often cast up on sandy shores. 
The sexes are easily distinguished. In the male the cheli- 
peds are enormously elongated, and the pleon is very 
small and has only five joints, although it is quite plain 
that the central one of the five is in reality a compound of 
three that have coalesced. In the female the pleon, though 
small, is broader than in the male, and has the seven joints 
distinct ; the openings of the vulvze can without difficulty 
be observed on the plastron between the third pair of legs ; 
