HELIX. 317 



very oblique, lunate ; outer lip simple or expanded, columella long,, 

 concave, not thickened within, its edge reflexed. Type H. pomatia 

 L., Frontispiece, fig. 7; (see also pi. 44, figs. 6, 7, H. asemnisvar. 

 vetusta). 



Animal large with wide fleshy foot, the sole undivided ; above 

 coarsely gran ose- reticulate ; right and left facial grooves strongly 

 marked ; labial tentacles well developed ; mantle edge bearing a 

 bluntly rounded right body lappet and a similar left one, the latter 

 either continuous or interrupted over the back, but reappearing in 

 a broad rounded lobe on the left side. Top of tail rounded, with a 

 subobsolete median line or none ; back from mantle to head with a 

 pair of longitudinal grooves. (Frontispiece, fig. 7, If. pomatia). H. 

 aperta, H. aspersa and other species examined show the same exter- 

 nal characters. 



Jaw strong, arcuate, with several stout ribs denticulating both 

 margins. Radula (pi. 67, fig. 11, H. pomatia) with well developed 

 ectocones on central and lateral teeth ; marginals with bifid inner 

 and small simple outer cusps. 



Genitalia: Penis short, passing into a short epiphallus upon 

 which the retractor is inserted, the epiphallus ending in a long flagel- 

 lum and vas deferens. Dart sack unusually large, containing a 

 four-bladed dart, the blades long, separated from the coronated base 

 by a neck or constriction (pi. 61, fig. 11, aspersa; fig. 15, pomatia). 

 Mucus glands usually divided into several branches subdividing 

 into very numerous fingers, but sometimes (H. aperta, asemnis) the 

 number is as low as four or five. Seminal receptacle globular, on a 

 long, nearly straight duct, which usually bears a diverticulum. 

 Hermaphrodite duct much knotted ; hermaphrodite gland compact. 

 (Frontispiece, figs. 5, 6, H. pomatia, Oberau, Bavarian Tyrol. PI. 

 61, figs. 12, 15, H. pomatia. PI. 61, fig. 9, H. asemnis. PI. 61, figs. 

 13, 14, 11, H. aspersa). 



The typical Helicogenas agree with the types of Otala and with 

 Tachea vindobonensis in having the mucus glands divided and sub- 

 divided into many "fingers"; but as in Otala and Tachea, this is 

 an inconstant feature, the number being 4 or 5 in some species. 

 The main character of the group is its globose shell, and this offers 

 a perfectly tangible sectional feature. The dart sack is larger than 

 in the related sections except Tachea. There is usually a diverticu- 

 . lum developed on spermatheca duct, but in H. pomatia and some 

 other species it is generally absent. 



