90 THE NAUTILU3. 



One of the features, however, considered characteristic, and from 

 which the generic name was derived, is not constant. The beaks are 

 not always capped, or calyculate, and in C. transversa,e. g., they are 

 simply rounded, as a rule, while in all other species, examples with 

 rounded, not calyculate, beaks, are occasionally found, and some- 

 times at a large percentage. As stated elsewhere, it seems that this 

 is caused, at least partly, by the seasons during which propagation is 

 effected. 



It has been asserted, and repeated, that the Calyculinae have a 

 cyclical period of life, within one year, depositing their young in 

 spring. This seems not to hold good. Of Col. transrersa Say, e. g., 

 I have collected specimens at all stages of growth, and also gravid 

 animals in all seasons, also in midwinter, and nearly the same can be 

 said of C, partumeict, truncata and securis. And among materials 

 sent for examination from different places and collected at various 

 seasons, the mussels were found of different ages and sizes. 



Since the publications of T. Prime and Clessin, little has been 

 said about our Calyculinas. During the last eight years I had 

 chances to examine many thousands of specimens, ow r ing to the 

 efforts and the kindness of a number of conchologists. Yet the 

 materials extant are still insufficient, especially from the Southern 

 and Western States. Most of the species seem to be rather variable, 

 and some considerably so, in regard to size, shape, surface appear- 

 ance and color, and some forms could be referred to certain species 

 only after careful examination and often repeated comparison, and 

 even then doubtfully in some instances. More materials from many 

 localities are very desirable. 



They preferably inhabit quiet waters, to which they are best 

 adapted, with their thin and fragile shells. Pools, ponds, ditches, 

 slow rivers and creeks often abound with them, where they are 

 crawling among plants and dead leaves. In fast running streams, 

 with coarse bottoms, they are scarce, and so along the shores of 

 larger lakes. 



So far as 1 know them now, the species are the following: 



1. C. elevata Hald. A southern species, with comparatively 

 strong shells. The specimens are not always so high and of such 

 circular outlines as in T. Prime's figure. A rather small, but well 

 inflated form from Kansas sems to range under this species. 



2. C. contracta Pr. Seems to be a good species. Seen from 



