350 Memoirs of the Indian Museum. [Vol. V, 



mon on the east coast of India and grows in great luxuriance on the stone-work of 

 Madras Harbour. The distribution extends from Hong Kong to the Arabian Sea. 



Modiola undulata (Dunker). See p. 358. 



Modiola striatula, Hanley. See p. 360. 



Family Arcidae. 



Area (Anadara) granosa, Linn., Lamy, J own Conch., LV , p. 210 (1907). Plate 

 xvi, figs. 3-6. 



Shells are abundant in a subfossil condition at the head of Rambha Bay, on 

 Barkuda I. and at many other places in both parts of the lake ; but the animal is ex- 

 tremely scarce in a living condition. Living and fresh specimens with the epidermis 

 still complete were taken on only three occasions, — off Samal I., off Kalidai and near 

 Barkul, in March and September. The largest of these is only 26 mm. in breadth, 

 whereas a large shell from the Nicobars exceeds 75 mm. The subfossil specimens are 

 intermediate in size, not exceeding 50 mm., while shells of about this size were seen 

 with the epidermis still present in the outer channel in March. 



We have referred above (p. 339) to von Neumayer's observations on a dwarfed 

 form of this species that occurs in a subfossil condition in the Yang-tse-Kiang delta. 

 A. granosa is frequently found living in brackish water on the coasts of India and 

 Malaysia, but the larger specimens in the Indian Museum all seem to come from 

 marine localities. It may therefore be assumed that dwarfing is correlated in this 

 species with decrease in the salin^ of the water ; in the Chilka Lake the process 

 seems to have been progressive and to have commenced while the south end of the 

 lake was still in communication with the sea. The case is one of the best illustra- 

 tions with which we have met, of the gradual change that has taken place in the 

 fauna of the lake in the course of its comparatively short geological history. 



The species has a distribution extending from the Arabian Sea to Japan and 

 Australia. 



Area {Fossularca) lactea, Linn., Lamy, Journ. Conch., LV, p. 97 (1907 j. 



A few living specimens were dredged in the channel between Satpara and Bar- 

 hampur I. in March and a dead shell was taken at the same locality in September. 

 They occurred on a bottom of muddy sand.. It seems probable that the species is 

 killed off annually towards the close of the monsoon by the irruption of fresh water. 

 A. lactea is a common European and E. Atlantic mollusc and has been recorded from 

 Ascension I., S . Africa, the Red Sea and various Indian localities; also somewhat 

 doubtfully from the Philippines. 



Family Erycinidae. 



Kellya chilkaènsis ,* Preston, 1915, p. 298, figs. 10, 10«. 



This species is apparently scarce, but living specimens were found in both parts 

 of the lake, — near Kalidai and Patsahanipur in March and in the inner part of the 

 outer channel, both in this month and in September. 



