new lirachyuroiis Crin^tacean. 541 



of tli« I;irp;ei" dactyliis is inncli enlar;^ecl and directed obliquely 

 backwaiuls. 



It is ill the Cyinopoliidre, however, that we find more 

 cliaracters in common, for in CymojwJia the carapace is 

 square and flat, especially in certain species sucli as G. whitei, 

 and, although the arrangement of the furrows does not agree 

 in detaihs, a certain general resemblance with them can l)e 

 traced. The form of the Literally elongated orbits in Cyino- 

 polia, with their deeply-cut upper margin and the prominent 

 outer orbital teeth, also suggests our crab ; and it may be 

 added that some of the legs, although not the last pair, are 

 flattened for swimming. The front, however, is very different, 

 showing no trace of deflection, but having a median emargina- 

 tion and a thin edge. 



On the whole, though the indications of affinity are 

 conflicting, it seems probable that Cymopnlia is the nearest 

 relative of this Cretaceous crab, with possibly some relation- 

 ship to the Portunidte. Though Cymopolia is now usually 

 placed in the Catometopa, the fact that its systematic position 

 was till recently the subject of discussion increases the likeli- 

 hood that it may be the survivor of a primitive group still 

 showing traces of divergent affinity with widely diiferent 

 groups. 



In conclusion, I wish to thaidc Di-. F. A. Bather, F.R.S., 

 and Miss M. J. llathbun for their assistance, and also 

 Dr. W. T. Caiman, F.K.S., who not only gave me access to 

 the collection of recent crabs in his charge, but helped me in 

 other ways. 



EXPLANATION OF THE PLATES. 



Carcineretes tcoohicotti, geu. et sp. n. 



Pi.ATK xvr. 



Fiy. 1. Diirsal view of almost coniplete male sholl, with tin- ambulatory 

 appendages on the left side. Ilolotype, B.M., In. 20780. 



Plate XVII. 



Fiy. 2. Abdominal view of same. 



Fiy. 3. Dor.<al view of anotiier male shell, with the right minor chela the 



only one of the appendages preserved. H.M., In. L'0781. 

 Fig. 4. Abdominal view of same. 

 Fiy. 5. Anterior view of .^anie. 

 Fiy. 0. Left major chela of another Bpecimen. J^.M., In. 20782. 



Fig. 1, X 2 diam. ; Figs. 2-G, x Ij diam. 



