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- 
lusea, or by worms and the burrows of Cliona. 
“Some of these I have now the pleasure toexhibit. 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. 
“Tt is that of aspecimen of Pinnxotheres which has been entombed 
in a cyst of pearl by a living pearl-mussel, into the shell of which 
he had ventured to intrude. 
**Tt seems extraordinary and beyond belief that the Meleagrina 
should of all the Conchifera 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, Pectunculus, and at 
least some half-dozen other bivalves, with whom it appears to live on 
the most friendly terms. 
“Tt 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 
Pinnotheres, 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 alargeseries of Pinnotheresin the Museum: the one from 
Australia is referred to P. orientalis, but as these are all females 
comparison is useless. These are from shells of Pinna, Donax, and 
Pectunculus. ‘There are others from Broken Bay. 
“ Prof. Dana, U.S. Expl. Expedition, 1852, part i. text, pp. 380— 
381, and Atlas, pl. 24. fig. 3, describes a species under the name of 
P, obesa from Fiji Islands. The male, however, is said to be slightly 
broader 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 63 broad.) 
“Mr. Willett’s specimen is slightly longer than broad, and in size 
agrees very nearly with the male of P. pisum, which was formerly 
deseribed by Leach as P. latreillei.” 
The following papers were read :— 
