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PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



the concomitant enlargement of the first (or first and second) 

 admedian. Of the two species most prevalent in this country 

 excentrica exhibits the large admedian best, and costaia the small 

 central. The first three or four basal plates are sub-quadrate. The 

 admedians liave the sliape of a capital L, i.e. there is a diastema 

 between niesocone and ectocone. This is characteristic of many 

 Pupidoe. One or two rows of transitiouals are present ; there are 



three typical admedians in excmtrica and four in costata. The 

 externals (not counting the first or last) have six rounded pectinations 

 in excentrica and four in costaia. They have a strong lateral and 

 posterior inclination, the basal plates being obtuse-angled parallelo- 

 grams. The more median cones are considerably larger th;tn the others. 

 CcBcilioides acicula has a somewliat similar radula; but here the 

 admedians have well-developed endocones, wliich do not occur in any 



Helicid, so far as I am aware. The externals also are more numerous, 

 oblong, and regularly pectinated, if one may use that term in describing 

 cones so extremely short and rounded. Nevertheless, the resemblance 

 seems very well wortli noting. 



In AcANTHiNULA WO also have scjuared admedian basal plates. The 

 admedians number six or seven. The most salient character is the 

 curved combined median and anterior margin of the external 



