SKENEA. 65 



mouth placed below the spire, and more or less detached from 

 the body- whorl : operculum many-whorled, with a central 

 nucleus. 



Although the definition of this genus by its founder, 

 Dr. Fleming, is extremely vague (" spire depressed, and 

 destitute of spinous processes'"), common usage has 

 established it. It originally contained three so-called 

 species, viz. S. depressa, S. serpuloides, and S. divisa. 

 The first of these (or S. planorbis) is the type and sole 

 representative; the other two are synonymous, and belong 

 to the genus Cyclostrema. More species were afterwards 

 added, but doubtfully, by Forbes and Hanley; these 

 have now been assigned to what I consider their proper 

 places. The tongue of Skenea is very much like that 

 of Rissoa. 



The present genus is partly Delphinoidea of Brown. 



SKENEA PLANOK/Bis*,!Fabricius,5 ^'"] ' 



Turbo planorbis, Fabr. Fn. Groenl. p. 394. 8. planorbis, F. & H. iii. p. 156, 

 pi. Ixxiv. f. 1-3, and (animal) pi. GGK f. 1 & la. 



BODY greyish- white : snout rounded and gibbous ; tentacles 

 long and widely divergent ; they are not, as in Rissoa, setose : 

 eyes seated on broad and scarcely raised protuberances : foot 

 truncated in front and rounded behind ; sole marked down the 

 middle of the posterior half with a slight groove or line. 



SHELL resembling in shape a miniature Helix ericetorum, thin, 

 opaque, and seldom glossy : sculpture, only a few slight and 

 obscure puckers in the line of growth : colour reddish-brown, 

 or pale tawny : spire scarcely visible, unless viewed edgewise 

 or with the mouth of the shell towards the observer ; apex 

 blunt and rounded : whorls 4, rather loosely coiled ; the last 

 much larger in proportion to the others, and occupying at least 

 three-fourths of the shell : suture deep : mouth projecting out- 

 wards, with a sharp and somewhat flexuous edge ; umbilicus 

 forming a wide, open, and rather deep funnel, usually exposing 

 the interior of the spire : operculum clear-white, concave, with 



* Flat-coil. 



