EMARGINULA. 259 



Genus II. EMARGFNULA * Lamarck. PL VI. f. 3. 



Body conical : mantle protruded from the slit in front of 

 the shell, outside which it forms a short tubular process : foot 

 studded at the upper side with papillae : verge cirriform, on 

 the right-hand side. 



Shell cap-shaped, with a vertical slit in front, which is 

 partly filled up as the shell increases in size, so as to leave a 

 furrow : beak always spiral : inside thickened on each side of 

 the slit. 



These pretty shells, commonly called " slit-limpets/'' 

 inhabit Europe, Asia, Africa, America, and Australia. 

 The very young resembles a Scissurella ; it has a regular 

 Trochoidal spire, and the outer edges of the slit are 

 inflected : the fry has no slit. 



1. Emarginula Fiss'uRAt, Linne. 



Patella fissura, Linn. S. N. p. 1261. E. reticulata, F. & H. ii. p. 477» 

 pi. lxiii. f. 1 (as E. Millleri). 



Body white, sometimes faintly tinged with yellow or light 

 brown : mantle open in front; margin finely ciliated; tubular fold 

 forming an entrance into the branchial cavity, fringed outside 

 with minute papillae : head large and broad, usually protruded 

 beyond the foot : tentacles contractile and therefore varying in 

 length, flattened at the sides : eyes oval, placed on round pe- 

 duncles one-third of the way up from the outer base of the 

 tentacles : foot oval, crested above on each side ; round the 

 upper edge of this crest, and near its junction with the rest of 

 the body, is a row of small milk-white papillae or tentacular 

 processes. 



Shell usually raised, so as to give a height in proportion 

 to the length as 2 to 3, solid, opaque, not glossy : scidjoture, 

 25-35 strong but narrow and cord-like ribs, which radiate 

 from the beak to the margin, and as many smaller interme- 

 diate ones ; sometimes these ribs are equal in size ; they are 

 crossed by from 20 to 30 somewhat slighter concentric ribs, 



* Haying a little notch in the margin. t A cleft. 



