20 DR. NELSON ANNANDALE ON 



Peninsula, and is the form found in ponds and sluggish streams in 

 the province of Singgora. 



The eggs are laid about Christmas or the beginning of the 

 year, as soon as the rains cease. They are exposed some feet above 

 the surface of the water on tree-trunks, posts or the stems of reeds, 

 and are formed into oval masses about the size of a small hen's egg. 

 As they are of a pure white colour they are very conspicuous. The 

 individual eggs are about 6 mm. in diameter but are pressed so 

 closely together that they are usualh^ distorted. Only 

 those in the centre of the mass are fertile or contain yolk, those 

 that cover it externally being reduced to dry scale-like bodies, 

 which protect the true eggs. The scale-like aborted eggs are absent 

 from the base of the mass where it is in contact with the surface to 

 which it is attached. In spite of the protection thus afforded, the 

 fertile eggs are. sometimes parasitized by a small wasp. The var. 

 lacustris has the same habits of oviposition and often attaches its 

 egg-masses to limestone cliffs. Whether other Siamese species or 

 varieties produce egg-masses of the same type I do not know. In 

 the common Indian P. globosa and P. carinata the eggs are laid in 

 a shallow depression in damp ground at the edge of water. They 

 form a feebly coherent mass and are all normally constituted and of 

 a spherical shape. In Bengal the eggs are laid after the rains 

 break, about July ; but in Madras I have found them rather later 

 in the year. 



Race lacustris, nov. 



I propose this name for a form found at the edge of the 

 inner or freshwater region of the Tale Sap or Inland Sea of 

 Singgora. The spire is still smaller (and flat at the apex) and the 

 body-whorl still broader and more oblique than in shells of the var. 

 subampullacea from the same district. The surface is also more 

 irregular and more frequently eaten away. The colour of the shell 

 is also as a rule darker and rougher, but this majr be due to the 

 more frequent growth of minute. algae on the surface. 



Measurements (in millimetres) and Proportions of Shells. 

 Height ... 78 75 67 



JOURN. NAT. HIST. S0C. SIAM. 



