DECAPODA. BRACHYURA. 549 



Fam. 7. Corystidae. Sternal plastron narrow ; 2nd antennae with 

 long flagella ; 3rd maxillipeds narrow, usually not operculiform. Corystes 

 Latr., carapace longer than broad ; C. casaivelaunus (Perm.). Markings 

 on carapace resemble a human face ; chelipeds very long in male ; the long 

 flagella of the 2nd antennae, applied together, form an afferent channel 

 for the respiratory water, when the animal lies buried in sand ; when it is not 

 buried the current can be reversed ; front rostrate in the young. Common 

 on our shores, where it is often cast up by the sea. Nautilocorystes and 

 Pseudocorystes M.-Edw. closely allied. Atelecyclus Leach, with operculi- 

 form 3rd maxillipeds, and Thia Leach are British. Th. polita Leach 

 ( = residua Herbst) with polished carapace and abdomen narrow in both 



