THE NATURAL HISTORY SURVEY 271 



inner cusp and the eleventh and all that follow are of the usual 

 form (Fig. 87). 



Genitalia: Not examined. 



Distribution: New England to California and Hudson Bay 

 to Louisiana; Alaska (Randolph). 



Geological distribution: Pleistocene; Loess. 



Habitat: Found in small colonies in ditches and clear 

 patches of swamp. It prefers submerged pieces of wood. 



Remarks: This species is distinguished by its heavy spiral 

 lines and long, acute spire. The animal is very rapid and de- 

 cisive in its movements. Several specimens, kept together in 

 captivity, ate holes in each other's shell for the lime for their 

 own shells. This was at first attributed to cannibalism, but 



Fig. 87. 



Radula of LIMN^A CAPERATA Say. (Original.) c, central tooth; 1-7, 

 lateral teeth; 8, 9, modified marginals; 10, first true marginal; 12, 14, 17, 

 intermediate marginals; 20, 25, outer marginals. 



upon investigation this supposition was found to be incorrect. 

 It is quite abundant and is one of the neatest Limnasids found 

 in this area. An egg mass of this species was laid March 16, 

 1897. I* contained forty-five eggs, distinctly nucleated, and in 

 a jelly-like mass measuring 1 1 by 2 mill. 



On March i8th a second egg mass was laid, and on the 

 igth three more masses. On the 22d three individuals were seen 

 in coitu, each one endeavoring to play the active part. Of the 

 five egg masses laid each contained the following number of 

 eggs: 42, 42, 35, 45, 28. The eggs were spherical in shape and 

 very distinctly nucleated. One set of eggs was laid the morn- 

 ing of the igth, and at noon of the 20th embryos were seen 

 slowly rotating about, propelled by numerous cilia. The 

 writer regrets that through some accident which occurred while 



