234 Dr. W. Stimpson on the Classification of the Brachyura, 



may well require the closest scrutiny before acceptation. For 

 example, he says, " The Leucosice I consider to include only 

 Dana^s Leucosidea, with Dorippe and ^thma. I separate the 

 Calappida and Matutidce from them, and unite them with the 

 Parthenopina rejected from the Oxyrhyncha." This combination 

 is justified " by the agreement in the situation of the afferent 

 canal of the branchial cavity and of the male sexual organs," &c. 

 But the Calappida are entirely removed from the Parthenopina 

 in the structure of the mouth-parts ; the buccal cavity is nar- 

 rowed anteriorly so that the eJ0Perent branchial channels termi- 

 nate at the middle instead of the sides of the endostome, and 

 are covered by the indurated summits of the lacinise of the 

 first pair of maxillipeds (tritocheirognathites). Like the Leuco- 

 sidea they are oxystomatous, as Milne-Edwards has shown. 

 They, indeed, difibr from these latter in the situation of the 

 efiferent canals, and should therefore be separated as a distinct 

 group ; but they should no more be united to the Parthenopina 

 than should the Dorippida, which Dr. Strahl would unite with 

 the Leucosidea, although these are far more nearly allied to the 

 Calappida, not having the afi'erent canal covered by the exognath 

 of the outer maxillipeds, which is the case in all Leucosidea. 



Again, Dr. Strahl remarks, " The genus Grapsus, limited by 

 the rejection of Leptograpsus, Metopograpsus, &c., and repre- 

 sented by the species Pharaonis, strigosu^, Webhii, &c., must be 

 removed not only out of the Grapsoidea, but even entirely out 

 of the Brachyura, because the structure of the external an- 

 tennae differs completely from that which prevails amongst the 

 Brachyura. Grapsus, for instance, has no operculum at the base 

 of the external antennse, but a perforated tubercle, as in the 

 Macrura, and must therefore at least be placed among the 

 Anomura." Here we would have Leptograpsus variegatus and 

 Grapsus strigosus, for instance — forms so closely allied that they 

 are placed in one and the same genus by so skilful a naturalist 

 as Dana — separated so widely from each other that the latter 

 species is placed among the Anomura ! Let us examine fresh or 

 wet specimens to ascertain whether Grapsus in reality has, at the 

 base of the antennse, a structure so essentially differing from 

 that found in ordinary Brachyura. Dried specimens are too 

 commonly used in these investigations, and are very apt to lead 

 to error. The " operculum " spoken of above is the coxal joint 

 (coxocerite) of the external antennse, which is moveable in all 

 crabs, even where the next (basicerite) is not. In a Maia, for 

 example, this coxal joint may be raised a little, so that the mem- 

 branous areola* which occupies its postero-interior surface may 



* The so-called tympanum. It is very doubtful whether the auditory 

 orgau is ever here situated. Kroyer has demonstrated (Kongl. Dauske 



