HELIX. 321 



deflexed in front, tumid. Aperture wide-lunar, oblique ; lip ex- 

 panded and thickened within, the baso-columellar margin straight, 

 widened by a blade-like callus within, flattened and adnate. Sur- 

 face smoothish. Type H. nemoralis L., pi. 44, figs. 4, 5. 



Animal showing a pair of longitudinal grooves on back and indis- 

 tinct right and left facial grooves, elsewhere coarsely granular ; sole 

 very indistinctly tripartite; mantle-edge with small right and 

 minute left body-process on each side of breathing pore. 



Jaw (pi. 67, fig. 1, H. nemoralis, Wurzburg) solid, arcuate, with 

 4-6 strong ribs grouped in the median part and denticulating either 

 margin. Radula having the middle cusps only developed on cen- 

 tral and lateral teeth, the side-cusps represented by a slight lateral 

 wave, but in some forms they are present and minute. Marginal 

 teeth having the inner cusp long, oblique and bifid, outer cusp small, 

 simple (pi. 67, figs. 2, 3, H. nemoralis'). 



Genitalia: penis long, bearing a long flagellum ; duct of sperma- 

 theca very long and usually with a diverticulum. Dart sack mus- 

 cular, containing a four-bladed dart, with conspicuously coronated 

 base and long head, the blades split in some species. Mucus glands 

 two, inserted on opposite sides of vagina immediately above d. s.> 

 each subdivided into several long, slender cylindrical finger-like 

 caeca (pi. 63, fig. 12, H. nemoralis). 

 Distribution, entire Europe. 



Tachea is one of the most conspicuous and characteristic forms of 

 European snail life. They live on bushes and walls, in gardens, 

 vineyards, etc., and, while avoiding the direct rays of the sun, are 

 light-loving creatures. They colonize freely, H. nemoralis increases 

 rapidly where introduced in America. H. hortensis inhabits many 

 of the islands off the New England coast, and being found in pre- 

 Columbian kitchen-midding deposits, cannot be regarded as a recent 

 immigrant. Possibly it may be the sole survivor of that Viking 

 incursion in the eleventh century. 



The variations of the Tacheas are mostly in coloring, and it has- 

 not been considered worth while to give below the multitude of 

 names founded on band-variations, etc. There is considerable vari- 

 ation in the size of dart sack, and in the darts of various species, as 

 well as in the number of fingers of the mucous glands, which are 

 generally quite long (15-16 mill, in nemoralis, splendida, coquandi^ 

 29 in vindobonensis), and vary from four in each group in nemoralis, 

 to from 16 to 30 in vindobonensis. 

 21 



