30 PALUDINA SUBPURPUREA. 



distance within the margin, being upon the 

 right side. It will scarcely be confounded with 

 another organ resembling the point of a tenta- 

 cle, situated near the external base of the left 

 tentacle. 



The foot is described as short in front; but 

 although this is the case (in the genus) when 

 the animal is in a state of repose, it is far 

 advanced when in motion; and it is a singular 

 fact that the rostrum of the animal is not 

 advanced at the same time, the latter indeed, 

 being scarcely ever visible. 



EXPLANATION OF PLATE 9. 



Figures 1 and 2 are taken from an adult specimen in 

 the cabinet of the Academy of Natural Sciences; 3 and 4 

 represent half-grown shells. 



