ODOSTOMIA. 171 



[like the tentacles of all other species of Odostomia], simulate 

 ear-shaped folds ; tips but slightly developed : eyes very black, 

 not quite close to each other, and placed a little behind the 

 inner bases of the tentacles : foot long (often extending on the 

 'march to the antepenultimate whorl) and very thin, square in 

 front and expanding at the corners into rather sharp-pointed 

 auricles, behind which it is gradually constricted towards the 

 upper part of the body, and terminates in a narrow slender and 

 acute point. (Clark.) 



Shell forming an attenuated and somewhat cylindrical cone, 

 rather thin, semitransparent and of a polished lustre : sculptMre, 

 none to the naked eye or when examined with a hand lens, 

 although, by appljdng the microscope with a high power, spiral 

 striae similar to those observable in 0. ^cilice may be here also 

 detected : colour clear white or glassy in live specimens, milk- 

 white in dead ones : sjnre gradually tapering to a blunt point ; 

 nucleus like that of the last species : luJiorls 8-9 (besides the 

 nucleus), regularly increasing in size ; they are usually flat- 

 tened, but never angulated ; the last occupies from nearly half 

 to a third of the shell : (future very narrow, slightly excavated, 

 somewhat oblique, and margined in the manner described in 

 my account of other species : mouth irregularly and obliquely 

 rhomboidal, contracted or narrow above and expanded below ; 

 length about one-fourth of the spire : outer lip gently curved 

 on the lower part, shelving or sloping downwards from a little 

 below the periphery : inner Up imperceptible above the pillar, 

 slightly reflected and straight (but now and then recurved or 

 twisted) below : umhilicus none : tooth or fold rarely developed : 

 operculum thin, and most delicately striated, with a very short 

 spire. L. 0-175. B. 0-05. 



Var. 1. turris. Shell of nearly equal breadth throughout, 

 with rather convex whorls. Farthenia turris, Forbes, in Rep. 

 Br. Assoc. 1843, p. 188. 



Var. 2. ventncosa. Shell of a thinner or delicate texture, 

 with tumid whorls and a deep suture. Parthenia ventricosa, 

 Forb. I. c. Eulimella affinis, F. & H. iii. p. 313, pi. xcviii. f. 7. 



Yar. 3. obeUscus. Shell smaller and narrower, with more 

 compact whorls. 0. oheliscus, Jeffr. in Ann. & Mag. N. H. 

 3rd ser. i. p. 46, pi. ii. f. 5. 



Habitat : Sand, with an admixture of mud, in the 

 coralline zone, on different parts of the British coasts ; 



i2 



