JEFFREYS I A. 59 



slight plication at the base/^ In Grave's classified list 

 of the Mollusca^ published in 1847^ Rissoella is given 

 as a synonym of Oclostomia. 



1. Jeffreysia dia'phana'^j Alder. 



Rissoa? glabra (afterwards R. ? dia'phana^. Aid. in Ann, N. H. xiii. p. 325. 

 pi. 8. f. 1-4. J. diaphana, F. & H. lii. p. 152, pi. Ixxvi. f. 1. 



Body pale yellowish- white, faintly tinged with fleshcolour, 

 and of a granular texture: snout expanding into two club- 

 shaped lobes or processes, which diverge at the same angle as 

 the tentacles, but are shorter and smaller : tentacles cylindri- 

 cal, compressed (both the false and true tentacles are covered 

 with vibratile cilia. Alder) : eyes rather distinct than large, 

 sessile and placed far back on the neck "v\ithin the shell ; each 

 is encircled by a slight integument, so as to appear raised : 

 foot lanceolate, somewhat bilobed in front, and angidated at 

 each corner, rounded or bluntly pointed behind: opercular 

 lobe mottled with brown, extending a little beyond the edges 

 of the foot. 



Shell forming a rather short and oblique cone, very thin, 

 quite transparent, and of a somewhat iridescent lustre : sculp- 

 ture, apparently none, but under a good magnifier consisting of 

 dehcate although obscure spiral striae ; the lines of growth are 

 equally microscopical, but finer and more numerous : colour 

 whitish: spire having a blunt and abrupt point: luhorls 4|, 

 convex, gradually enlarging ; the last occupies three-fifths of 

 the spire; first whorl rounded: suture deep: mouth rather large : 

 outer lip sharp, iucm^ved above, rounded and slightly expanded 

 below : inner lip rather flexuous, its outline being accommo- 

 dated to the curve of the pillar ; behind it is a narrow umbi- 

 lical chink : operculum yeUowish-white, depressed in the centre, 

 composed of 4 or 5 segments or layers, which are indistinctly 

 defined, and closely striated in the same concentric dii^ection ; 

 the inner side forms a very obtuse angle, the opposite side 

 being rounded ; spike triangidar and flattened, having its nar- 

 rower end at the base ; medial rib short, diverging from the 

 spike at a right angle ; rib on the inner side marginal and 

 shght. L. 0-075. B. 0-05. 



Habitat : Delesseria hypoglossum and various other 



^ Transparent. 



