THE NACTJLUS. 129 



M. Southwick, Curator of the Roger Williams' Park Museum, 

 Providence, R. I. 



Key to the Bertmidian Species of the Genus Cerithium. 



The species of this genus were the hardest to revise owing to the 

 fact that the descriptions being brief and often inaccurately figured, 

 no two museums have them named alike. A generous use of the 

 microscope is necessary to distinguish species, and while there are 

 undoubtedly intergrades, the majority are I think, distinct species 

 and not varieties. They are so dissimilar that they can he readily 

 separated. Most of the species may be picked up in Bermuda by 

 the thousand. I brought home at least a half bushel for studv. 



o ^ 



A. Very small, jet-black inside and out, often decollate, nodules 

 in vertical rows of three dashes. Bermuda form, Fig. '25 ; Haiti 

 form, Fig. 26 ; white-tipped Florida form, Fig. 27. 



C. tn/'niuinin Gmel. 



B. Larger, stouter, plain black or dirty brown inside and out, 

 spirals very uneven, nodules in vertical rows of tliree dots 

 (Fig. 28). C. nigrescens Mke. 



C. Shell stout, spirals uneven, handsomely variegated black and 

 white or yellow and white, nodules in vertical rows of three 

 dots (Fig. 29). C. variablte Ads. 



Note. This shell has been called eriense Val., and even 

 placed as a variety of ferrugincum Say, which it does not re- 

 semble in the least. (See the original figure and description 

 offerrugineum by Say.) 



D. Long, narrow, yellowish-brown, spirals very irregular, tliree 

 vertical nodules united, forming vertical ribs, by far the rarest 

 form in Bermuda (Fig. 30). C. ferrugineum Say. 



E. Long, narrow, apex sharp, black with a white revolving band 

 below the suture, the black band contains dashes and the white 

 band dots, spirals regular, blackish inside (Fig. 31). 



C. septenstrialum Say. 



F. Larger than any of the above, spirals regular. A whitish 

 calcarious deposit distinguishes this shell (Fig. 32). When 

 this covering is removed by acid or wear as in Fig. 33, it re- 

 veals a brownish interior with white bands on which the 

 nodules are shaped like an exclamation point (!), the two 

 upper dots being united. The apex is always very sharp. 



G. albocoopertum sp. n. 



