382 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



rufescens. As cantiana, except -central (see plate) ; externals 



truncate. 

 caperata. As virgnta ; externals minute. 

 Itala. As virgata, but externals sometimes acute. 

 harhara. Yarious, as plate ; not irregular. 

 granulata. Rounded ; rounded ; rectangular. 



(c) Shape of lower edge of basal plate. 

 virgata. Slight incurvations. 



cantiana. Notched ; irregularly notched ; straightened. 

 revelata. All slightly incurved. 



sericea. All slightly incurved ; transitionals more incurved. 

 hispida. Yery slight incurvation. 

 rufescens. Straight ; incurved ; straight. 

 caperata. Double curve ; curved ; irregular. 

 Itala. Incurved ; various ; irregular. 



larhara. Double outward curve ; various ; slightly incurved. 

 granulata. Incurved ; straightened ; straightened. 



{d) Shape of apex. 



See plate. The pointed form, as in Itala, is found in transitionals 

 of several species, especially sericea and hispida. Incurvation or 

 acumination in central is partly a matter of thickness or thinness 

 of growth. 



(/) Number and character of cones visible. 

 virgata. 3 ; 2 ; 2. 



cantiana. 3 ; 2 ; 2 ; accessories evanescent. 

 revelata. 3 ; 2 ; 2. 

 sericea and hispida. 3 ; 2 ; 2. 

 rufescens. 3 (ectocones minute) ; 2 ; 2 or 3. 

 caperata. 3 ; 2 ; 4 (3 if bifid mesocone be secondary). 

 Itala. As caperata, but second accessory external oi'ten missing. 

 Barbara. 3 ; 2 ; 3 to 5. 

 granulata. 3 ; 2 ; 4 or 5. 



Diagnostic Notes. 



In ca^itiana the admedians approach those of hortensis and nemoralis 

 in respect of rotundity. The shape of the basal plates distinguishes 

 cantiana from virgata. Revelata shows remarkably shortened and 

 squared unci and plates ; in sericea and hispida both are lengthened. 

 The pointed apex shown in sericea is characteristic, but not so marked 

 in immature specimens ; it is due to a general strengthening and 

 thickening of the backbone of the mesocone, if we may so speak. 

 The ' knife-blades ' (external mesocones) of these two species differ in 

 slenderness, and further variations are found in other forms belonging 

 to the same group. Those of rufescens are uniformly narrower. The 

 base of the cusps in this species is larger, and it will be observed 

 that where enlargement occurs it seems first to appear in this region ; 

 compare the figures oi pomatia and its allies. The bifid mesocones of 

 externals mark the remaining four species here described ; in Itala this 



