158 Records of the Indian Museum. [Voi.. XIII, 



rapidly over or through the sand and so is able to recover its posi- 

 tion and foothold whenever dislodged from its temporary burrow. 

 Its favourite mode of progression is to protrude the foot consider- 

 ably, bend it into a deep curve with the point pressed against the 

 sand close to the shell, then by suddenly straightening the foot 

 the shell is jerked in the opposite direction. By a variation of 

 the movement it can also throw its shell over upon the opposite 

 valve. 



With increase of size^ individuals gradually move to more 

 sheltered sands and become sluggish and sedentary in their habits. 



Spawning occurs about the beginning of September at Tutico- 

 rin ; probably also about May. 



It is common in the outer channel of the Chilka Lake, in the 

 Cuddalore estuary (S. Arcot), at the entrance to the Silavathurai 

 Lagoon, Tuticorin, in the delta of the Tambraparni, and near the 

 mouth of the river at Tellicherry in Malabar. I have also col- 

 lected it in the sub-fossil condition from shell-pits in the Surla 

 swamps of the Sonapur backwater, Ganjam, and from the sub- 

 fossil shell strata at Korampalara, Tuticorin; there is little doubt 

 that it lives at the mouths of the majority of estuaries and back- 

 w^aters in Southern India. The type form and the variety im- 

 pudica, both pale in colouring, are about equally common at 

 Chilka and Tuticorin, i.e. on the East Coast. In the Tellicherry 

 river the dark-coloured heavy-rayed variety aurora is the only 

 form seen. 



In addition to the foregoing, numerous examples of this shell 

 from other localities are present in the Indian Museum collections 

 submitted to me for identification ; the particulars are as 

 follows : — 



Tavoy Coast, Burma (M. 398). 11 shells, comprising 6 of the type, i of var. 



impiidica, i var. castaiiea, 2 var. zonaria and i var. morphina. 

 Malacca (M. 10487/2). All of type form. 

 Arakan (M. 10851/2 and M. 10855/2). 5 of var. impitdica, and 1 small one 



of type form. 

 False Point, Orissa (M. 10845/2). 2 small specimens. 



Trincomalie, Ceylon (M. 10842/2). 5 of var. casta)iea, 1 oi var. tmpudica. 

 (?) Andamans (M. 10858/2). One fine example of var. ivipiidica. There 



appears to be some doubt as to the origin of this shell as this is queried 



upon the label. 

 Bombay (M. 10836/2). 5 shells comprising 3 of var. imp/idica, i of var. 



ciisfaneu, and i of the type form. 



{a) Type. 

 (Plate V, fig. 13.) 



1835. Cytherea meretrix, Lamarck, Aiiiin. sans. Veyt., 2nd ed,, Vol. 

 VI, p. 300. 



By removal of all forms distinctively or peculiarly coloured, 

 we get a numerous residue which may be considered as represent- 

 ing the generalised central form, the type assemblage of the species. 

 When the periostracum is present, the ground colour varies usu- 

 ally from a pale to a dark grey ; frequently as at Chilka Lake it 

 is of a pale straw colour, at others a light rufous yellow. This 



