THE NAUTILUS. 



Vol. XXXII. JANUARY, 1919. No. 3 



NEW FORMS OF CAECUM IN NEW ENGLAND. 



BY EDWARD S. MORSE. 



A few years ago I collected from several scoops of sand from 

 Easton's Beach, Newport, R. I., over two hundred specimens 

 of Caecum. From the variety of forms discovered, not includ- 

 ing the three New England species * which were more or less 

 abundant, one might imagine that the Marquis de Folin had 

 been wrecked off the coast of New England at this place and his 

 collection of Caecidae had been washed ashore. In de Folin' s 

 monograph of the group he says that the species vary greatly 

 among themselves. The same species may vary from a smooth 

 to a ribbed surface, not only that but the three sub-genera 

 established by Carpenter 2 under the names of Elephantulum, 

 Anellum and Fartulum are not based on permanent characters. 



A reference to Carpenter's monograph of Caecidae shows that 

 he gave little value to his groupings, for he says "The groups 

 described under Caecum can scarcely be regarded even as sub- 

 genera, so very gradually do they pass one into the other ; but 

 they are found convenient, to avoid the frequent repetition of 

 characters, and to aid in the identification of species." He 

 does not give a single illustration, which greatly diminishes the 

 value of the monograph. 



Bearing in mind this dictum of de Folin, one might believe 

 that here is a distinct group of mollusks in which permanent 



1 C. pulchettum, Stimpson. C. coopcrii, Smith. C- johnioni Winkley. 

 1 Proc. Zool. Soc. of London, 1858. 



