136 PYRAMIDELLIDJE. 



in front, a little in advance of the foot : tentacles rather long 

 and leaf- like, with blunt tips : eyes very small, placed close 

 together on the middle of the neck between the tentacles at 

 their inner base : foot rather broad, more or less indented (and 

 now and then deeply bilobed) in front, obliquely truncated and 

 irregularly bilobed behind. 



Shell forming a somewhat cylindrical cone, strong and 

 solid, semitransparent and glossy : sculpture none, unless ex- 

 amined with a magnifying-power, when the surface appears 

 covered by fine and regular spiral strise ; the periphery is 

 slightly keeled : colour pale yellowish- white or whitish, with 

 a dark border below the suture in each whorl as in many other 

 of the smooth and semitransparent species : spire rather long, 

 turreted, and abruptly terminating ; nucleus exposed, usually 

 twisted forwards : ivkorls 5-6 (besides those composing the 

 nucleus) , convex, and gradually enlarging ; the last forms one- 

 half of the spire, and scarcely exceeds the next in breadth : 

 suture narrow, but well defined : mouth squarish, not much 

 expanded or angulated at the inner base ; it is proportionally 

 small, and its length is scarcely a third of the whole spire : 

 outer Up projecting but little beyond the periphery, below which 

 it is considerably incurved towards the pillar, thus contracting 

 the mouth : inner lip thin, and adhering to the pillar on the 

 upper part, without joining the outer lip. thickened, reflected, 

 and gently curved on the lower part, the basal angle being 

 usually slight : umbilicus none : tooth small, not prominent, 

 nor very conspicuous : operculum of a thinner texture and less 

 strongly striated than that of 0. cono'idea or the last species. 

 L. 0-125. B. 0-05. 



Yar. striolata. More conical, with a shorter spire and larger 

 mouth ; the periphery is bluntly angulated ; the tooth is 

 stronger, and prominent ; and the spiral strioe are unusually 

 distinct. 0. striolata, (Alder) F. & H. iii. p. 267, pi. xcv. f. 5. 



Habitat: Under stones and in rock-pools at low-water 

 mark, and among seaweeds in the laminarian zone ; it is 

 widely distributed and not uncommon. A specimen of 

 the variety was found by Mr. Alder in shell-sand from 

 Ilfracombe ; Mr. Norman has taken it in Bantry Bay, 

 and Mr. Hockin at the Land's End. I noticed the typical 

 form in the Royal Museum at Copenhagen (from the 



