72 THE NAUTILUS. 



sect larvse and their cases had in many instances formed a thick 

 mass over the entire surface of the shell, completely closing the 

 aperture, thus causing the animal within to die. Scarcely a 

 living individual could be found that was not more or less in- 

 fested in this manner. 



Burr-oak trees stand near the margin of the water, and the 

 acorns which had fallen from them in the water were often 

 brought out with my little hand-dredge together with cockle- 

 burrs, in company with the infested shells. The cockle-burrs 

 were often difficult to distinguish from some of the shells, 

 covered as they were with the larvse cases. 



When closely observed, I noticed that the majority of the 

 dead shells were lying on the bottom of the pond with aperture 

 up; some could be seen lying in this manner with but a slight 

 opening remaining in the aperture, in which I could see the yet 

 living animal struggling for freedom. 



A few living ones were to be found on the vegetation grow- 

 ing in the water which were in all stages of infection. 



I revisited the pond in the fall, after the warm weather, and 

 found a few living shells and plenty of recently dead ones; but 

 scarcely a vestige of the insect cases was to be seen anywhere, 

 thus showing that they flourish during the hot weather and 

 after maturing the cases soon decayed, leaving no trace of the 

 perpetrator that so rapidly devastated the colony. T. VAN 

 HYNING. 



POLYGYRA PLAN A BAHAMENSis Van. n. var. This variety is 

 distinguished from the typical P. plana (Dkr.) of Bermuda by 

 frequently having a spiral internal lamina as in P. cereolus car- 

 penteriana (Bid.) of Florida. The surface of the spire has finer 

 sculpture than P. carpenteriana (Bld.'s) arid a trifle coarser than 

 the typical P. plana (Dkr.). 



The types are in the collection of the Academy of Natural 

 Sciences of Philadelphia, being tray number 44463, from Cur- 

 rent Settlement, Eleutha, Bahama Islands, collected by Mr. C. 

 J. Maynard in 1897. 



The Academy's collection contains other specimens of this 

 variety from New Providence and Inagua Islands. E. G. 

 Vanatta. 



