THE NATURAL HISTORY SURVEY. 329 



Animal: Color yellowish-white on foot and body; head 

 and rostrum black with several yellow or golden-yellow spots, 

 the tip of the rostrum yellowish-white. Rostrum rather large, 

 rounded. Tentacles long and filiform, the black eyes placed 

 on swellings at their lower outer base. The body appears 

 speckled with black and yellowish-white through the shell. 

 Foot wide, rather short, slightly auriculated before, whitish on 



FIG. 116. 

 Operculum of BYTHINIA TENTACULATA Linnet (Original.) Enlarged. 



edge with a yellowish part near the center and toward the an- 

 terior end. Cervical lobes (lappets) round, wide, short, rather 

 fully extended. Verge rather large, placed as usual in the 

 family. Operculum placed toward the posterior part of the 

 foot, calcareous within, concentric; the rings of growth stand 

 up in the form of ridges or scales, and their arrangement is 

 quite regular (Fig. 1 16). The foot measures 6.50 mill, in length 

 and 4.00 mill; in width. 



Radula formula: ^ + ^ + ^ + ^ + 1. + ^+^ (3- i -3); 

 central tooth wider than high, ends produced and rounded, 

 lower edge concave and with a rounded process extending 

 from its center; lateral lobes armed with six to seven denticles 



FIG. 117. 



Radula of BYTHINIA TENTACULATA Linne. (Original.) C. central 

 tooth; 1, intermediate tooth; 2, 3, lateral teeth. 



which are rather long and roundly pointed, the denticulate 

 portion extending from just beneath the reflection to the end 

 of the lobes; reflection wide and low, seven-cuspid, the center 

 cusp large and roundly pointed and the lateral cusps sharply 

 triangular; intermediate tooth squarish, the lower outer corner 

 produced; reflection wide and low, seven-cuspid, the third cusp 



