BY THE REV. J. E. TENISON-WOODS, F.G.S., &C. 807 



MOLLUSC A. 



This list is meant to include only the freshwater mollusca found 

 -within the lake or the river Pansipit. 



1. Cyrena sub-orbicularis, Van d. Busch; Philippi, Abbil- 

 •dungen und Bcschr. neuer Conch. Bd. III. p. 77, pi. li., fig. 1., 

 1849. A somewhat solid sub-orbicular shell, with a distinct 

 posterior undulation extending from the umbones to the margin. 

 It is covered with an olive-green, shining, neat periostraca, which 

 projects in concentric asperities along the lines of growth, which 

 are crowded. It is not much eroded, and has altogether a cleaner 

 appearance than most members of the genus. Very common in 

 all the ditches and stagnant waters about Manila, Laguna de 

 Bay, &c. 



2. CoRBicuLA CROSSEANA, Petit. A small tumid shell with 

 regular rounded sulcations, covered with a brownish olive perios- 

 traca, underneath which the shell is purple, especially at the 

 umbones, where it is eroded. The transverse ribs between the 

 sulci are I'ounded. The enormous quantities of this mollusk are 

 indescribable. Along the river Pasig there are duck farms 

 extending for many miles on both banks, and maintaining hun- 



'dreds of thousands of ducks. They ai-e almost entirely fed on 

 the river mollusca, and principally on this Corbicula. At Los 

 Banos, in the Laguna de Bay, where the boiling springs from 

 Maquilin empty themselves into the lake, there are large heaps 

 ■of these shells destroyed by the hot water, together with a 

 Paludina to be mentioned presently. The lake mollusks are also 

 sold in the markets as food for fowls. They are brought down 

 in bags by the passenger steamers which ply upon the lake. 

 Nevertheless, there seems no diminution of the supply ; in fact, 

 this continued clearing off of the surplusage would seem to have 

 a happy effect in giving room for the fullest development of the 

 young mollusks. I have been informed that the supply, if any- 

 thing, is increasing. 



