210 PKOCIOIiDINGS OF THE MALACOLOGICAL SOCIETY. 



(e) Lacinia parallel with lower edge of basal plate or otherwise. 

 {No entry means that the lacinia is 'parallel.') 

 Pisana. External almost coincident. 



hortensis. External almost parallel with outer side of basal plate. 

 nemoralis. As hortensis. 



aspersa. Admedian lacinia angulate ; external irregular. 

 arbustorum. Central and admedian not parallel (diagonal). 

 lapicida. Conspicuously at right angles to central axis, not following 



the curves of the margin. 

 ohvoluta. Central and admedian diagonal ; external coincident. 



(/) Number and character of cones visible. 



Pisana. 3; 3; 2 (mesocone bifid). 



hortensis. Eounded tongue-shaped point, narrower base ; as central, 

 but more quadrate base ; 2 (mesocone bifid). 



nemoralis. 1, blunt, thick, angular at summit; as central; 2 (bifid 

 mesocone and conical ectocone ; sometimes additional ectocones). 



fomatia. 3 ; 2 ; 2 (bifid mesocone, but not rarely found entire). 



aspersa. 3 (mesocone ovate and overlapping others) ; 3 or 2 

 (endocone only apparent, really part of mesocone) ; 2 (meso- 

 cone bifid; ectocone rarely duplicated). 



arbustorum. 3 (long pointed mesocone, small curling ectocones) ; 

 2 (as central) ; 2 (mesocone bifid ; sharp, especially ectocone). 



lapicida. 1 ; 1 ; 2, but ectocones frequently duplicated. 



ohvoluta. 1 (slight notches representing side cones) ; 1 (a slight 

 notch representing ectocone) ; 2 (claw-like bifid mesocone). 



It is hoped that the above additional characters may serve for 

 the differentiation of the species in detail ; they are therefore tabulated 

 under characters, and not primarily under species. In comparing such 

 minor points allowance must be made for individual variation. 



It remains to summarize what appear at present to be the points of 

 diagnostic value ; the tables will be found to contain much more, if 

 further confirmation be needed in any case. 



Selicogena pomatia is remarkable for showing very little diminution 

 of size in the external unci. The radula is very broad in comparison 

 with that of aspersa. The endocones of the external unci are so little 

 prominent as to be hardly noticeable at first sight. 



Helicogena aspersa is characterized by the presence of distinct, though 

 small, accessory cones. 



Euparypha Pisana has these cones very distinct, otherwise being- 

 planned very much on the same lines as Helicogena. 



The CepcBce have the accessory cones absent or obsolescent in mature 

 specimens : nemoralis has normally a trifid apex, hortensis a bifid one. 

 The basal plates of hortensis are much longer in proportion than those 

 of nemoralis. 



Arianta is marked by the exceptional length of the cones, and yet 

 more clearly by the arcuate shape of the basal plates. 



PTelicigona cannot well be confounded with those just named. The 

 cones in all regions are very obviously rounded, and the basal plates 

 partake of the same character. 



