THE OYSTER-CEAB 101 



was no longer especially necessary. That the crab may 

 be at times useful to the mollusc seems after all not so 

 very improbable, for at the approach of an enemy so 

 nervous a creature as a crab would no doubt begin to 

 scuttle about and in this way communicate its terror to its 

 more apathetic companion, which would then naturally 

 close its doors against the danger. Dr. H. Woodward has 

 recently recorded a remarkable instance of a Pinnotheres 

 found encysted in a pearl-like formation of the pearl- 

 oyster, Meleagrina margaritifera. 



Vinnotlieres veterum, Bosc, and Pinnotlieres jyistim 

 (Linn.) are common European and British species. Giard 

 and Bonnier suppose that under the latter name several 

 distinct species have been confounded. Its Zoea, long ago 

 studied and drawn by Mr. Vaughan Thompson, is a 

 singular-looking microscopic object. Among the names 

 of other species some which indicate the animal's resi- 

 dence may be mentioned, as Pinnotheres ascidiicola^ Hesse, 

 from the coast of France, the Japanese Pinnotheres fho- 

 Iddis, de Haan, and Pvmwtheres lithodomi, Smith, from the 

 Pearl Islands and Lower California. A similar indication 

 is given in the generic name, Holothuriaijhikis^ Nauck. 



In ' The Civil and Natural History of Jamaica,' when 

 speaking of a Pinnotheres, which he calls the Oyster-Crab, 

 Patrick Browne says : ' This little species is generally 

 found with the Mangrove oysters, in their shells, where 

 they always live in plenty, and spawn at the regular 

 seasons ; and such as eat the oysters, do not think them a 

 bit the worse for being accompanied with some of these 

 crabs, which they swallow with the fish. They are very 

 small and tender, and nearly of the same length and 

 breadth, seldom exceeding a quarter of an inch either 

 way.' 



Hymenosoma, Desmarest, 1823, was established under 

 a name invented by Leach, and signifying a membrana- 

 ceous body. This is a character in which many members 

 of the family partake. Hymenosoma orbiculare, Latreille 

 and Desmarest, is a South African species. Halicarcinus, 

 White, 1846, is closely allied to Hijmenosoma^ but courts 



