1886.] IN MELEAGRINA MARGARITIFERA. 177 



his partners on the N.W. coast of Australia, and has submitted 

 many shells to me which had been attacked by lithodomous Mol- 

 Insca, or by worms and the burrows of Cliona. 



" Some of these I have now the pleasure to exhibit. I have, more- 

 over, to-day been permitted by Prof. Flower to examine a still more 

 interesting specimen which he has just received from Henry Willett, 

 Esq., F.G.S., of Arnold House, Brighton. 



" It is that of a specimen of Finnotheres which has been entombed 

 in a cyst of pearl by a living peai'l-mussel, into the shell of which 

 he had ventured to intrude. 



" It seems extraordinary and beyond belief that the Meleagrina 

 should of all the Concliifera be the one to resent the commensalism 

 of the Pea-crab, which has been known since the days of Cicero, 

 Pliny, Oppian, and Aristotle to inhabit the shell of the Pinna and 

 the Oyster, and has been recorded from Astarte, Feclunculus, and at 

 least some half-dozen other bivalves, with whom it appears to live on 

 the most friendly terms. 



" It is the females, however, which constantly reside within the 

 shells of the Conchifera, whilst the males are said to avail them- 

 selves of favourable opportunities to visit the females in their 

 retirement. 



" "Whether or not in this case the unlucky male intruded himself 

 upon Meleagrina at an unfavourable period, and finding no female 

 Finnotheres, penetrated so far beneath the mantle of the Pearl-mussel 

 as to be unable to retreat, one thing is quite clear, namely that the 

 Meleagrina entombed the intruder in a cyst of pearl from which the 

 clever pearl-button maker alone liberated him. 



" There is a large series o( Finnotheresin theMuseum : the one from 

 Australia is referred to F. orientalis, but as these are all females 

 comparison is useless. These are from shells of Finna, Donax, and 

 Feclunculus. Theie are others from Broken Bay. 



" Piof. Dana, U.S. Expl. Expedition, 1852, part i. text, pp. 380- 

 381, and Atlas, pi. 24. fig. 3, describes a species under the name of 

 F. obesa from Fiji Islands. The male, however, is said to be slightly 

 hroader than long, and the eyes (which in the adult female are quite 

 hidden beneath the overreaching and protuberant carapace) can be 

 seen in the upper view, and the front of the carapace is emarginated 

 by the orbits. (Size 4| lines long, and G| broad.) 



" Mr. Willett's specimen is slightly longer than broad, and in size 

 agrees very nearly with the male of F. jjtsum, which was formerly 

 described by Leach as F. latreillei." 



The following papers were read :- 



