68 CRUSTACEA. 



antice transversus vel arcuatus, nunquam rostratus. Epistoma bre- 

 vissimum. 



V. CRUSTACEA LEUCOSOIDEA. 



I. Via efferens medium palati trajiciens; area buccalis plus minusve 

 triangulata. 



II. Pyramis branchialis 7-9 branchiis instructus. 

 Discrimina III., VI., ut in Maioideis. 



V. Carapax sive transversus sive subglobosus. Frons angustissi- 

 mus. Epistoma nullum. Antennae minutae. 



The Maioidea pass into the Cancroidea through the Parthenope 

 group, the species of which are mostly transverse in form, with a short 

 epistome, and have the first joint of the outer antennae situated more 

 inward than the eyes, and rarely produced beyond them, besides being 

 either free or bounded commonly by a distinct suture on the outer side, 

 and occup3'ing a hiatus in the orbital margin, in all of which points 

 they differ from the Maia type. 



The Cancroidea pass into the Corystoidea through the genus Cancer 

 (Leach), and Pirimela, which have the outer maxillipeds projecting 

 somewhat over the epistome. Pirimela has also the narrow form of 

 the Corystoidea. But neither genus has the outer antennje of Co- 

 rystes. There is also a passage into the Anomoura through Acantho- 

 cyclus, in which the form is circular, the outer antennas obsolete, and 

 the branchiae less than the normal number; the line through Acan- 

 thocyclus leads to Corystoides and Bellia, genera of inferior grade, 

 approaching the Macroura in having no fossettes for the inner an- 

 tennas, although Brachyural in form. 



The Cancroidea and Grapsoidea are united, through Eriphia and 

 Telphusa on one side, and the Gonoplax group on the other. Tel- 

 phusa, although Grapsoid in form, has the same number of branchiae 

 as in the Cancroidea, a similar abdomen, and a like position for the 

 male appendages, and belongs properly therefore with the Cancer 

 group. In Gonoplax and some allied genera, the outer maxillipeds 

 are Cancroid in character, and unlike the other Grapsoidea, the 

 male verges are, in some cases, inserted in the basal joints of the 

 two posterior legs, instead of the sternum; yet they are conducted 

 in a channel in the sternum and so pass beneath the abdomen 

 instead of being covered by the abdomen from their insertion, as in 

 Telphusa and the true Cancroids. 



