neio Species of CoraJ-infestiiig Crab. 213 



V itli or closely allied to Crijploifurus coraUiudytcs. Culinau 

 bas shown that Hajxilocaiciuus and Crijptuchirus must be 

 placed in the same I'amily, nnd for this has proposed the 

 name lIai)alocarciiiida', in pla(.'e of A. Milnc-Edwards's term 

 " Lithoscaptcs," as the latter is based on a synonym of 

 Cri/pfoc/iii us, the later described of the two genera. 



The females of Ilopa/ocarciiius and Cri/ptochints agree in 

 their elongated form, and in the possession of a more or less 

 extended semi-membranous abdomen, which forms a brood- 

 pouch for the eggs; in the former genus the abdomen is 

 loosely bent under the ccphalothorax, while in the latter, 

 owing to its greater extension, the eggs are freely exposed 

 below. In both genera tliere are striking peculiarities in the 

 external (third) maxillipedes, which are widely separate, and 

 thus leave a considerable portion of the enlarged buccal 

 cavity exposed. The ischial joint is wide and has a large 

 rounded internal lobe, while the merus is greatly reduced 

 and resembles the three terminal joints ; the exopod is 

 reduced to a rudiment. In spite of superficial resemblances 

 to certain of the Anomura, the position of the female sexual 

 openings on the sternum shows that the family must be 

 relegated to the Brachyura. The general elongation of the 

 body is evidently an adaptation to the narrow space in which 

 the crab is confined, and the greater exposure of the eggs 

 than is usual in the Brachyura, is perhaps due to the increased 

 difficulties which would be experienced in their aeration, and 

 diminished need for protection in such an unusual dwelling- 

 place. The general softness of the integument, more [)articu- 

 larly of the abdomen, in both genera, is a feature which tin v 

 share Avith many of the burrowing or specially protected 

 forms. 



^^hile the male of Hapalocarcinus is still unknown, that of 

 Cryptochirus is noteworthy for the great reduction in size 

 vhicli it has undergone, and this is particularly the case in 

 the new species about to be described, a reduction wliieh is 

 probably an adaptation to the peculiar habitat, ^ylth the 

 female ensconced in a tunnel-like cavity closed at one end, 

 from whicli she is unable to escape, reduction in the size of 

 the male would obviously be of great advantage to the 

 species ; but so little is known as to the relation of the 

 female crab to the dwelling, that her inability to exhibit free 

 movement in the tunnel can only be conjectured. Further 

 observation is necessary to dcterjuiue whether or not each 

 female is generall. accompanied by a male, but it seems 

 highly probable that the male, on account of his. small size, 

 is able to pass freely from one tunnel to another. While 



