LIMNiEUS. 171 



Shell variable in form, more or less broad, rhomboidal- 

 ovate when the spire composes a full fifth of the dorsal 

 length, obovate subtrigonal when it is so short as barely 

 to fill a sixth of that space ; shining, horn-coloured both 

 within and without, manifestly and comparatively coarsely 

 wrinkled lengthways, with the spiral lines or interruptions 

 also distinct. AVhorls four to four and a half, somewhat 

 planulately shelving towards the obliquely curved suture ; 

 spire extremely short, and small ; its turns of very rapid 

 longitudinal increase ; the minute apical coil and the 

 moderately high and much tapering antepenult volution 

 together not equal in area to a fifth of the penult turn ; 

 the latter small-based in proportion to the body, which pro- 

 jects above on its right, and has its basal declination more 

 or less gradual and not much rounded. Mouth occupying 

 from three-fourths to four-fifths of the ventral length, and 

 from four-sevenths to almost two-thirds of the area, of a 

 somewhat rounded oval figure ; outer lip extremely ])yo- 

 minent, jutting out above almost at right angles to the axis 

 previous to the sweep of its uninterrupted arcuation, ad- 

 vancing towards the middle, receding anteriorly, expanded 

 throughout, especially below, which gives a projecting 

 look to the anterior dorsal extremity. Pillar lip elongated, 

 bending to the left, much reflected, not appressed, but 

 disclosing a more or less open umbilical chink : its left 

 edge much incurved; columellar twist more or less strongly 

 marked. Length an inch (or even more), breadth about 

 a fourth less. 



In the immature variety {acutus) the mouth is much less 

 capacious, and the body is very much smaller and nar- 

 rower in relation to the spire : the high and narrow turns 

 of the latter, and the anterior projection of the body are 

 still preserved. 



