58 HETEROPHROSYNID^E. 



species is frequently encrusted by the common Melo- 

 besia or nullipore in its earlier stage of growth. The 

 dark-crimson colour of the operculum offers a remark- 

 able contrast to the white shell of the 2nd variety. In 

 Erofessor TroscheFs ' Gebiss der Schnecken ' (vol. i. t. x. 

 f. 8) the lingual riband is represented as nearly similar 

 to that of Rissoa parva. 



Turbo ruber of Adams (from the Pembrokeshire coast) 

 appears to have been derived from a reddish specimen 

 of Rissoa parva, var. interrupta. Our shell is R. fulva 

 of Michaud, and Sabanaea Binghamiana of Leach. 



Genus II. JEFFREY'SIA*, Alder. PL I. f. 3. 



BODY slender : snout cloven so deeply that in some species 

 the lobes thus formed resemble a second pair of tentacles : 

 eyes placed behind the tentacles, on their inner side, either on 

 small bulgings or sessile. 



SHELL thin, smooth, and glossy: mouth oval or roundish- 

 oval, with a complete peristome : operculum rather thin, having 

 the nucleus on the middle of the inner side, and a short rib 

 on the under side, which proceeds from the nucleus in the di- 

 rection of the outer margin. 



The above characters show a greater departure from 

 Rissoa than those of the last genus. According to Mr. 

 Alder the lingual armature of Jeffreysia closely resem- 

 bles that of the common Rissoa ; and indeed we find 

 that the animals of both genera are vegetarians. Mrs. 

 Collings detected in the stomach of/, diaphana a species 

 of Lythocystis allied to L. Allmani. 



Dr. Gray makes this synonymous with his undescribed 

 genus Rissoella. The type indicated by him, in lieu of 

 a description, is Rissoa glabra of Brown, which is evi- 

 dently an Odostomia (probably 0. rissoides), having "a 



* A compliment paid to the author by his friend Mr. Joshua Alder. 



