92 Trans. Acad. Sci. of St. Louis. 



*125a. Elimia virginica multiline ata Say. Erie Canal. 



126. Elimia livescens Menke. 

 Station 10. Erie Canal (Walton). Very common in 

 water from six to eighteen inches in depth, on or in a soft 

 carbonaceous mud. Specimens are always covered with a 

 deposit of algae in this locality. The specimens collected are 

 ver}' uniform. 



*126a. Elimia livescens depygis Say. Irondequoit. 



*127. Elimia semicarinata Say. Irondequoit. 



Family Bissoidae. 



Subfamily Bythiniidae. 



Genus Rythinia Gray. 



128. Bythinia tentacdlata Linn^. (Plate X, figs. 7-10.) 

 Stations 3, 4, 6, 9 and 15. Erie Canal (Walton). Very 

 common everywhere. 



A number of specimens were obtained alive, and the writer 

 is able to give a figure of the dentition from an American 

 specimen. The central tooth is rather broader than long, very 

 much lobed at either end, the ends of the lobes rounded. 

 The usual rounded projection from the center of the lower 

 surface is present. The reflection is short and wide and 7- 

 cuspid, the center cusp large and rounded and the three side 

 cusps short, triangular and very sharp. The denticles on the 

 lateral lobes are 6-7 in number and are bluntly rounded. 

 The intermediate tooth is squarish, produced at the lower 

 outer corner and 7-dentate, the third cusp from the left side 

 being large and roundly pointed, and the side cusps, two on 

 the left and four on the right, are small and acutely triangu- 

 lar. The lateral teeth are long and narrow and rounded at 

 their lower extremity. The reflections are short and wide, 

 the first 12 and the second 16 cuspid. The writer was 

 not, unfortunately, able to count the number of rows of teeth. 

 The writer regrets that he does not have access to European 

 publications, in which the radulaof this species is figured, for 

 comparison. 



