LIMNEA CATASCOPIUM. 9 



The animals of figs. 1 and 6 were taken from 

 the Delaware at Camden, and are thickly- 

 covered with Cercaria bilineata, Hald.; a para- 

 site which must be very annoying, when pre- 

 sent in such numbers, as in this instance. 



"It is with much hesitation that we adopt a 

 new specific name for this shell (L. catas- 

 copium), having always heretofore considered 

 it as the same with L. putris of Europe; as far 

 as we can ascertain, the principal difference 

 appears to be in the more oblique revolution 

 of the whirls in the European species, and the 

 more abrupt termination of the spire." — Say. 

 The area of the aperture is not as great, nor 

 is the labium as much expanded, as in the 

 analogue. 



Explanation of Plate 1. 



Figure 1 represents the animal at the moment of open- 

 ing the branchial cavity, to take in a supply of fresh air. 



Figures 1 to 9 represent different forms of L. catas- 

 copium, as restricted by Say; the specimens being all 

 from the Delaware, except those of 4 and 5; the latter is 

 a profile outline of the left side, showing the depth of the 

 umbilical emargination: 8, 9 show the form of the young: 

 and 10, 11, 12 represent the variety L. pinguis. 



The foreign analogue of this species is placed under the 



j 2 



