SKENEA. 65 



mouth placed below tlie 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 planor'bis"^^ Fabricius. 



Turbo j)lanorbis, Fabr, Fn. Groenl. p. 394, S. planorbis, F. & H. iii. p. 156, 

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



Body greyish- white : snout rounded and gibbous ; tentacles 

 long and widely divergent ; they are not, as in liissoa, 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 Helioo 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 occupj'ing at least 

 three-fourths of the shell : suture deep : mo?6^7j- projecting out- 

 wards, with a sharp and somewhat fiexuous edge; umbilicus 

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

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



* Flat-coil. 



