72 Contributions to Indian Malacology. 



about 12 : 7. In 8, celox it is 12 : 10| and in & pinna 12 : 9|.* The 

 last named species is of a totally distinct form, being much wider 

 posteriorly than in front, so that it is sub-trigonal in shape instead of 

 rhomboidal. Its posterior hinge teeth, also, are near the extremity, 

 and so oblique as to be almost parillel to the hinge line, while in its 

 smooth, thin epidermis, marked concentric sculpture, and convex 

 posterior subdivision of the valves, it differs widely from 8. delta?. 

 The ligament of 8. pinna covers a greater proportion of the length of 

 the area, (about §,) than does that of S. deltas. It is much narrower 

 in proportion to its length, as is indeed the entire area, corresponding 

 to the smaller tumidity of the valves. 8. celox approaches more near- 

 ly to the present species, but is thinner and much less tumid, has its 

 posterior hinge teeth more oblique and nearer to the extremity, and 

 differs widely in sculpture. 



8. deltas was found under stones in creeks, adhering by a byssus. It 

 was not met with near the sea. It is the first species of the genus 

 that has been found in brackish water, both of the forms described by 

 Mr. Benson being from large rivers far above the influence of the tide. 



Mr. Benson mentions the occasional occurrence of a raised rib in 

 front of the keel in 8. celox. I have several specimens, which I received 

 from Mr. Theobald, shewing this peculiarity. It differs entirely from 

 the flattened subobsolete rib of 8. deltce. 



Figures of all 3 species are added to illustrate the difference between 

 them. 



Family ANOMIAID^E. 

 No. 42, Anomia, sp. 



The specimens of this shell have unfortunately been mislaid. I 

 only obtained two or three specimens, and it is extremely difficult to 

 make out the species of this genus. 

 No. 43, Anomia (iEnigma) senigmatiea, Chem. 



Occasionally found adhering to stumps of trees in salt water creeks. 

 Family OSTRBID^F. 

 No. 44, Ostrea, sp. (? 2 sp.) 



A large form occurs in the creeks below low water mark. A 

 smaller kind is met with between tide marks in mangrove swamps and 

 creeks, attached to wood or stones. I unfortunately omitted to take 

 specimens of either. 



* Measured from authentic specimens of each species. 



