( 52 ) 



Abdomen well developed, soft, spirally coiled, with the terga thin and 

 widely separated. 



Eyestalks long and slender, the ophthalmic scales slender and approxi- 

 mated. Antennal acicle well formed, usually short : flagellum non-setose. 



External maxillipeds approximated at base: the exopodites of all 

 three pairs of maxillipeds are flagellate: the endopodite (palp) of the first 

 maxillae has a small recurved flagellum. 



Chelipeds unequal and dissimilar, the left being vastly the larger : the 

 fingers move in an obliquely vertical plane, and the finger-tips are calcareous 

 and much spooned. 



4th pair of legs subchelate, 5th pair chelate : both of them bear the 

 usual sub-terminal pavement of corneous imbricating granules, as also do the 

 appendages of the tail-fan. 



The abdomen has no paired appendages except those that form the tail- 

 fan : in both sexes there are on the left side (somites 2 — 5) 4 biramous 

 appendages, which, as usual, are largest in the female. The telson and caudal 

 appendages are more developed on the left side than on the right. 



The gills are phyllobranchiae and are 13 on either side, disposed as in 

 Pagtnopsis, Pagmistes, and Clibanarius. 



The hard parts of the exoskeleton have a dense porcellanous texture, 

 and as a rule are vividly variegated. 



Calcinus (as Bouvier has remarked) is ver}- closely related to Cli'yanarius, 

 differing only in the form of the chelipeds and the denser texture of the hard 

 parts of the exoskeleton. 



The distribution of the genus is practically the same as that of Clibanarius, 

 the species being found in tropical and subtropical waters all round the globe, 

 but having less tendency than those of Clibanariits to spread outside the 

 tropics. 



The majority of Calcini belong to the Indo-Pacific fauna, ranging from 

 the east coast of Africa and the Red Sea to California. Panama, and Chili, 

 but not going much beyond the parallels of 25'N. and 35*8. In the West 

 Indies and neighbourhood we find one (or three) species ; and one species 

 is known from the islands of the Western Atlantic (Azores to Cape Verde). 

 One of these Western Atlantic species (C. ornatus Roux) occurs in the Medi- 

 terranean, where indeed it was first discovered ; and to my mind it is a signi- 

 ficant fact — one of many similar facts that may assist us in our search for the 

 ancient boundaries (or open connexions) of the Mediterranean — that the 

 nearest relative of this species is the Indo-Pacific C. Herbstit. 



