Baker — Notes on a Collection of MoUusks. 16 



ZONITOIDES ARBOREUS Say. 



Alpena. Common and typical. 



ZONITOIDES NITIDUS Mullcr. 



Thunder Bay Island (very large); Sugar Island. Com- 

 mon. 



Family Endodontidae. 



Ptramidula alternata Say. 



Sugar Island; Sulphur Island. 



Specimens from the first-named locality are very light 

 colored, the red flames being faint and much broken. The 

 spire of many specimens is very high, an average individual 

 measuring 17 mill, in diameter and 11.50 mill, in height. 

 Specimens from Sulphur Island have a diameter of 22.00 

 millimeters. 



EXPLANATION OF PLATE. 

 Plate I. 



Figure 1-4. Lymnaea nasoni Baker. Types. 



" 6-6. Pkysa walkeri Crandall. 



" 7-8. Physa ancellaria crassa. Walker. 



" 9-10. Physa ancellaria crassa. Walker. Varitty. 



" 11. Planorbis bicarinatus striatus. Baker. 



" 12. Lymnaea woodruffl. Baker. 



*« 13-14. Lymnaea catascopitim Say. Variety. 



" 15-16. Lymnaea catascopium Say. Variety. 

 All figures enlarged three diameters. 



Issued, May 21, 1906. 



