ODOSTOMIA. 141 



17. O. dia'phana"^^ Jefireys. 



0. diaphana, JefFr. in Ann. & Mag. N. H. 2nd ser. ii, p. 341 ; Sowerby, 

 111. Ind. pi. 17. f. 23. 



Body brilliant frosted subhyaline-white : mantle forming a 

 conspicuous tubular fold at the upper angle of the apertui^e of 

 the shell : snout short, cloven in the centre almost to the eyes ; 

 each segment or lobe has an outward curve equal to an angle 

 of 40° : tentacles strong, rather long, without much auriform 

 folding, roundish and taper, terminating in minute circular 

 snow-white inflated tips ; instead of the tentacles moderately 

 diverging on each side of the snout, they are widely curved 

 and carried at a right angle to the axis of the shell : eyes close 

 together, at the internal basal angles of the tentacles : foot 

 long, broad, and thin, rather concave in front, slightly auricled, 

 and when fully extended reaching beyond the body-whorl in 

 front ; it terminates in a distinct bifurcation, which is very 

 apparent in slow march, but, on a quicker pace being attained, 

 the fork in some measure decreases in consequence of the 

 greater extension of the foot. (Clark ; as Chemnitzia ohliqua.) 



Shell inclining to spindle-shaped, very thin, nearly trans- 

 parent, and lustrous : sculpture none, except slight flexuous 

 and numerous microscopical striae in the line of growth : colour 

 whitish : spire rather long, abruptly truncated ; nucleus ob- 

 liquely declining and concealed, raised in front and twisted 

 backwards : ivJiorls 4, convex, and i'aj)idly enlarging ; the last 

 occupies two-thirds of the shell ; the upper part of each is 

 encircled by a thickened rim : suture narrow, but well defined, 

 and oblique : mouth rather oblong than oval, narrow and acute- 

 angled above, expanded below ; its length exceeds two-fifths 

 of the whole spire : outer Up fiexuous, retreating at the upper 

 corner of the mouth, where it forms a rather deep sinus, and 

 projecting in the middle: inner lip extremely slight on the 

 upper part, thickened, and gently curved, but veiy little reflec- 

 ted, on the lower part : umbilicus developed in the adult only, 

 when it is small and inconspicuous, being approached by a 

 narrow canal or groove from the base : tooth consisting of an 

 insignificant and retired fold : ojierculum extremely thin, ex- 

 cept on the inner side, light- yellow, scored obliquely by fine 

 and close-set flexuous lines, and having a distinct but short 

 and nearly terminal spire of two minute whorls ; it resembles 

 in shape a Cristellaria. L. 0*1. B. 0-05. 



* Transparent. 



