134 THE NAUTILUS. 



EXPLANATION OF PLATE X. 

 Variation in Planorbis campanulatus Say. 



Series a. Apical aspect. 



1. From fossil marl beds Mackay Lake, Ottawa. 

 2-8. From Blue Sea Lake, Quebec. 



Series b. Umbilical aspect of the above. 



Series c. Profile view, showing aperture of the above. 



Series d. Profile view, from side opposite aperture, of the 

 above. 



The four views of each specimen are shown in vertical rows, 

 e. g., the four figures at left of plate represent a single shell. 

 All figures natural size. 



ON THE LAND SHELLS OF MONROE, CONNECTICUT, 



BY ARTHUR JACOT. 



Twelve miles north of Bridgeport, Conn, is situated Monroe 

 Center. That part of the town of Monroe lying between the 

 Center and the Housatonic River was searched at several locali- 

 ties for terrestrial mollusca by my wife and me. This region pre- 

 sents five well-marked biological associations in which land 

 shells are common. Of these, the upland swamp ( 1 ) was found 

 to be richest in number of species and individuals. A tract 

 which has not been burned over for a great number of years 

 lying west of my father's house and barns (1) we considered to 

 be the best example of the upland swamp association. Water 

 can here be found throughout the year, though much less in 

 summer than at other times. The trees are mainly elm and 

 soft maple with clumps of black ash rising here and there from 

 the water. On each side of the wet area, among the maples and 

 elms are yellow birches, white ashes, and various swamp or 

 wet-land oaks. Lichens and mosses are very numerous, among 

 the latter being sphagnum. The cinnamon fern grows waist-high. 

 The dry wooded hill slopes to the south and southwest of this 

 tract represents the second (2) association, characterized by 

 Polygyra fraterna and Succinea retusa. The lowland swamp as- 



