THE NAUTILUS. 137 



more or less irregular in form, and usually deflected from the plane 

 of the rest of the whorls. 



P. campanulahLs Say. Common everywhere. An occasional 

 specimen has a hump on the last whorl opposite the aperture as 

 described by Case in P. multivolvis. 



P. campamUatus minor Currier. Distinguished only by it* 

 smaller size. Perch Lake, Kent County. 



P. albiis Mull. Commonly distributed over the State. 



P. exacuhis Say. This species which is found in all parts of the 

 State, varies considerably in size and color. 



P. defleetus Say. While not a common species, it undoubtedly 

 ranges over the whole State. 



P. parvus Say. Common everywhere and varies considerably 

 under local influences. 



P. costatus DeTar and Beecher. A minute costate form said to be 

 from the neighborhood of Ann Arbor. I know nothing of it. 



Segmentina armigera Say. Common everywhere. 



S. ivheatleyi Lea. (?) Found in great abundance several years in 

 the suburbs of Detroit. Has not been noticed elsewhere in the State. 

 This form if not Lea's Wheatleyi is easily separated from the typical 

 S. armigera by its thickened lip, which decidedly contracts the 

 aperture. 



Ancylus fuscus Ad. Although cited in all the catalogues from 

 that of Miles down, this species does not seem very common. Belle 

 Isle, in the Detroit river is the only locality where I have found it. 



A. rivularis Say. Cited by DeCamp. 



A. parallelus Hald. Northern part of the State. 



A. diaphanux Hald. River Rouge, Wayne County. Also citedl 

 by DeCamp. 



A. tardus Say. The most common species we have, judging from 

 my own experience. 



Valvata tricarinata Say. Common everywhere. The forms biear- 

 inata Lea, unicarinata DeKay and simplex Gld. are cited as distinct 

 by DeCamp. 



V. sincera Say. Very abundant in favorable localities all over 

 the state. The form known as striata Lewis, or Lewisi Currier, dis- 

 tinguished by its coarser striae and larger size, is cited as distinct by 



