HORNELL AND SOUTHWELL— PINNOTERES PLACUN^ 101 



Of the rest, 



10 individuals contained 1 female each ; 



2 „ ,, 1 female and 2 males each ; 



2 ' ,, „ 1 female and 1 male each ; 



1 „ „ 12 males ; 



1 ,, „ 11 males; 



1 ,, ,, 3 males ; 



2 ,, ,, 2 males each. 



Besides these particular individuals, a large number of others of the same age were 

 examined without note being taken of the exact numbers of pea-crabs respectively 

 contained ; scarcely any were found without one or more of these guests free within 

 the mantle cavity. The majority were located in the neighbourhood of the anus. 



Immature shells, as is natural, less frequently revealed the presence of commensal 

 pea-crabs ; when they did occur the crabs were more or less immature. It would seem 

 that the crabs grow towards maturity concurrently with their hosts. 



Placunse from Ceylon rarely contain this commensal. One large female was, how- 

 ever, taken by one of us some years ago from a large Placuna fished at Tampalakam- 

 Bay, proving the geographical range to extend from the Gulf of Kutch to Ceylon. 



A large number of Placunse obtained from Tuticorin in South India yielded no 

 pea-crabs. It would be interesting to learn the reason why these crabs are so 

 abundant in one locality, so rare in the others. Environment appears generally to be 

 identical in all three localities. 



Borrodaile, in his report on Marine Crustacea in "The Fauna and Geography of 

 the Maldives and Laccadives," vol. i., p. 428, refers to the Pinnoteridse as being 

 " small symbiotic crabs with very small eyes and orbits. Body usually more or less 

 rounded ; carpopodite of the third maxilliped does not articulate at or near the inner 

 angle of the meropodite. Body usually square or squarish. Male openings sternal." 



Laurie, describing a new species of Pinnoteres from the Gulf of Mannar (" Ceylon 

 Pearl Oyster Reports," vol. v.), characterises the carapace of Pinnoteres margaritiferce 

 as "circular, calcified, smooth and polished. It is flattened a good deal, though a 

 little convex." 



A specimen of Pinnoteres ahyssicola, Alcock and Henderson, was taken from a 

 living individual of a large species of lamellibranch {Lima indica, E. A. Smith) 

 dredged off the coast of Travancore at a depth of 439 fathoms. This specimen, 

 which was a female with eggs, had " the carapace as long as broad, circular and smooth. 

 The whole of the eyes and eye-stalks, and almost the whole of the orbits, visible in a 

 dorsal view." 



A specimen of Pinnoteres villasulus, Guerin Minivelle, found within the pearl 

 oyster in Torres Straits and presented to the Challenger staff [Challenger Reports, 



vol. xvii.) had the front "deflexed and trilobate." 



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