Baker — Notes on a Collection of MoUusks. 11 



and scalariform, while others are fat, with a short spire, but 

 all are distorted, more or less. They Eeiniud one of catas- 

 copium from Pine Lake, Charlevoix, Michigan. Two charac- 

 teristic measurements of palustris from this locality are given 

 below : 



Length 20.50; widli7.50; aperture length 8.00 ; width 5.00 mill. 

 " 15.50; " 8.00; " " 9.00; " 5.00 " 



Locality (2) produces a thinner shelled palustris which 

 varies toward the corpulent nuttalliana form. Some speci- 

 mens are heavily shouldered, while others are rather long and 

 narrow. The aperture is sometimes spreading and an um- 

 bilicus is not infrequently developed. Some measurements 

 of this form are given below : 



Lengli 23.00; width 9.00 mill. 

 " 22.50; " 11.50 " 

 «' 21.00; " 10.00 " 

 " 18.00; '' 9.00 " 

 " 23.00; •' 11.00 " 



At locality (7) the specimens are rather thin, light-horn 

 colored, with very heavy columellar fold. The specimens 

 from locality (5) are small and very solid, scalariform, with a 

 V ery heavy columellar pleit. 



A single reversed specimen was in the lot from Stony 

 Point. It consi.sts of four whorls and measures 9.50 mill, 

 in length. 



Lymnaea palustris nuttalliana Lea. 



Sugar Island; Sulphur Island ; Long Lake. 



It is a question whether nuttalliana can be varietally sepa- 

 rated from palustris. In the lot of shells from Sugar Island 

 there is an almost perfect gradation from typical palustris to 

 nuttalliana. Typical nuttalliana differs from palustris in its 

 larger size, more corpulent and swollen whorls, shorter spire 

 and very heavy columellar plait. The shells from this locality 

 are strong; but lio;ht. Monstrosities occur on the last whorl, 

 one specimen having a blind umbilicus. Many of the speci- 

 mens are strongly malleated. Some measurements of this 

 variable form are given below : 



