THE WINDOW-PANE OYSTERS. 



37 



Area r/iombea).* The results were chiefly negative. At Maram- 

 poddaturai, on the right bank, a hkely looking spot marked by a 

 fine " pasari maram," one living placuna was picked up in very 

 shallow water, measuring 157 by 143 ram. Nearer the head of this 

 backwater no more were found. 



Station VI. — In theKaddaiparichchan-aru about three-quarters of 

 a mile along this arm of the backwater, beyond the village of the same 

 name where there is a bifurcated coconut tree and past a slight bend 

 where weathered rocks Avith cleavage grooves jut out into the water. 

 Here the divers picked up and I subsequently measured upwards of 

 thirty dead and buried placunge with both valves complete. This 

 is a good example of an entire bed having been destroyed by natural 

 though catastrophic means, namely, mud-burial. In the subjoined 

 table I give a few selected measurements to show the range of size. 

 The insidious nature of the disaster which overtook this bed may be 

 imagined when it is stated that in several cases the delicate ear- 

 like lobes of the shell which occur on either side of the hinge 

 line, especially in young individuals, are still retained (text fig. 1). 



Fig. 1. — Left valve of a Placuna from the inside, fi'om a photograph X i 



I, I. Lobes of the shell, c. Hinge area, the longer cardinal tooth is 



posterior (the figure being reversed), m. Muscle-impression. 



This mollusc has red blood and dark red gills. 



-engtli. 



120 



94 



76 



Height. 

 110 



85 



64t 



f Left valve only. 



