ODOSTOMIA. 131 



deeply channelled or hollowed out lengthwise, and having a 

 spoon-shaped extremity: tentacles moderately long, and di- 

 vergent ; each has a flake-white longitudinal line in the middle, 

 running from base to point ; edges slightly folded ; tips less 

 white and inflated than in allied species : eyes rather close 

 together in the centre behind the tentacles : foot short, of a 

 more opaque white than the rest of the body ; it is excavated 

 in front, and so deeply divided or lobed as occasionally, when 

 fully extended, to present the appearance of a second pair of 

 short tentacles ; it terminates behind in a more or less obtuse 

 point. (Clark.) 



SHELL pyramidal, with a broad base, rather solid but semi- 

 transparent, and lustrous : sculpture, extremely fine and rather 

 numerous microscopical spiral striae, and still more minute and 

 close-set flexuous lines of growth ; a slight peripheral keel is 

 also observable in every stage of growth, but especially in 

 young and half-grown specimens : colour whitish, with a tinge 

 of pink or fleshcolour : spire gradually tapering ; nucleus ex- 

 posed and inverted on the back, in nearly a horizontal posi- 

 tion : whorls 6 (besides the embryonic ones), rounded although 

 compress"e*d~~compact and gradually enlarging ; the last occu- 

 pies about one-half of the shell : suture very narrow and 

 slightly excavated, sloping a little downwards in consequence 

 of the peripheral keel : mouth roundish- oval, contracted above, 

 and somewhat expanded but scarcely angular below ; its 

 length is less than a third of the whole spire : outer lip gently 

 curved, inflected just below the periphery : inner lip adhering to 

 the pillar above the tooth, and joining the outer lip at its upper 

 angle, slightly reflected and more or less curved below the 

 tooth : umbilicus developed and conspicuous, although small; 

 its entrance is through a channel behind the lower part of the 

 inner lip : tooth strong and prominent, placed just behind the 

 umbilical opening; in construction and extent it resembles 

 that of the last species : operculum yellowish-brown, finely and 

 closely striated ; the curved groove is unusually distinct. 

 L. 0-175. B. 0-075. 



Yar. umbilicata. Shell larger, stronger, and white, with a 

 broad base and usually a wider and deeper umbilicus ; peri- 

 pheral keel obscure. 0. umbilicata, Alder, in Trans. Tyneside 

 Nat. Field Club, i. p. 359. 



HABITAT : Coralline zone in various parts of the sea, 

 especially in South Devon. Cornwall, Dorset, the Chan- 



