HELIX. 



155 



Lingual membrane with 123 rows of 42—1—42 teeth each; 

 centrals long, narrow, with a long, acutely-pointed apex ; laterals 

 of same shape as centrals ; first uncini short, with two long, 

 coalescing denticles ; extreme uuciui with three short, obtuse 

 denticles. 



Fis. 266. 



Subgenus ACANTHINULA, Beck. 

 Shell perforated, globosely turbinated, with a brownish pli- 



cately-ribbed or aculeate epidermis ; whirls 4-5 ; aperture 



rounded ; peristome thin, somewhat expanded, its terminations 



approached. 



Animal (of H. harpa) small, compared to the size of the shell ; 



body and head slate color, eye-peduncles darker, short, thick; 



bulbous ; eyes large, distinct ; foot but two-thirds length of shell, 



whitish ; the body, disk, and mantle are marked 



with white dots, the edge of the mantle is of 



the same color as the head and eye-peduncles. 



The disk is rounded posteriorly, and broad and 



truncated anteriorly, the lateral borders are 

 deeply crenulated. The head is separate from 



the disk as in tlie Pupinse, bearing two minutely 

 crenulated lappets, which hang down on either side of the mouth 

 like a visor, reminding one of the oblique folds on the head of 

 Glandina truncata, which we believe to be homologous to them. 

 A longitudinal furrow extends from the mouth downward. The 

 body is so translucent that when extended the ganglionic centres 

 can be plainly seen. In motion they are exceedingly graceful, 

 at times poising their beautiful shell high above their body, and 

 twirling it around, not unlike the Phij.^a, again hugging their 

 pretty harp close to their body ; the shell, when in this last position, 

 continually oscillates as if the animal could not balance it ; it 



