"238 GEOMITRA. 



aa. Right eye-retractor passing to left of genitalia ; shell more 

 or less chalky ; lip simple or expanded, Helicella. 



? Geomitra. 

 This order of groups is reversed in the following pages. 



Genus GEOMITRA Swainson, 1840. 



= Geomitra SWAINS., -f- Plebecula, Helicomela, Lemniscia, His- 

 pidella, Spirorbula, Irus, Adinella, Rimula, Callina, Caseolus, Hys- 

 tricella, Discula, Tectula, Placentula, Ooronaria and Craspedaria of 

 LOWE, 1852-1854, + Ochthephila BECK, 1837, not Fallen, 1823. + 

 Heterostoma HARTM., 1841 to '44, -f- Turricula WOLL ASTON, 1878, 

 not of H. & A. Adams, 1856. 



Shell generally solid, rather cretaceous, unicolored or from one to 

 three banded : varying from globular or pyramidal to lens-shaped 

 or planorboid, the umbilicus open or closed. Aperture half-round 

 or circular; lip more or less expanded, at least at the columella, 

 usually thickened within, but having no lip-rib as in Helicella 

 columella dilated or reflexed. Type G. tiarella W. & B. (See pi. 

 68, figs. 1-19). 



Jaw low, slightly arcuate, with 15 broad, flat, crowded ribs in 

 tiarella, about 8 broad, separated ribs in lurida. In abjecta there is 

 a blunt median projection but no ribs. 



Radula (pi. 67, fig. 18, G. abjecta Lwe. ; pi. 70, fig. 40, G. 

 lurida Lwe.) having well-developed side-cusps on middle teeth, the 

 middle cusp about as long as the basal-plate. Lateral teeth bi- 

 cuspid. Marginals with the inner cusp long, oblique, and feebly 

 bifid, outer cusp bifid or even trifid. 



Distribution : Madeira group of islands. Only the most unsatis- 

 factory evidence exists to give ground for believing this genus to 

 occur outside of the Madeira group, except as occasional immigrants, 

 unless the occurrence of G. paupercula Lowe in the Azores and 

 Canaries be owing to natural causes. Those indigenous species of 

 the Canaries referred to Hispidella, Discula, Ochthephila, etc., may 

 better be left in Hygromia, Jacosta and other groups, until they may 

 be shown to actually have some characters of the Madeira forms. 

 The Canary Island Helix fauna is far more closely allied to that of 

 northern Africa than to that of Madeira. 



It would obviously be quite idle to discuss the origin or genesis of 

 this genus until its anatomy is made known. We are quite safe in 



