40 DR. GWYN JEFFREYS ON THE MOLLUSCA OF THE [Jail. 20, 



Distribution. Mediterranean from Gibraltar to Palermo, Madeira 

 {McAndrew), G.Mexico (Powr<a/(?«), Jamaica {Barrett); 18-117 

 fms. 



Fossil. Miocene : Calabria {Segiiema). Pliocene : (?) Biot, 

 Central Italy, and Sicily. 



Solarium aldrovatidi of Foresti is a variety. 



Deshayes proposed this genus in 1830 under the name of Omulaxis 

 or Omalalaxis, and in 1832 as Bifrontia. The former name, slightly 

 but necessarily altered in the spelling, must therefore be retained, 

 although Bifrontia is equally appropriate. But I am not satisfied 

 that the genus is distinct from Solarium. The shape of the shell, 

 and especially of the peculiar operculum, closely resemble those of 

 8. architce. The sculpture of the present species varies greatly'in 

 respect of the short longitudinal striae, which in some specimens are 

 strong and close-set, and in others are entirely wanting. The whorls 

 are often wholly or partly disjoined or are occasionally united. 



I. Adeorbis supranitidus, S. Wood. 



A. supranitidus, S. Wood, Mon. Crag Moll, in Pal. Soc. Publ. 

 1848, p. 137, t. XV. f. 5, a, b. 



Omalaxis supranitida, G. O. Sars, Moll. reg. arct. Norv. p. 214', 

 t. 22. f. 20, a-c. 



'Porcupine' Exp. 18/0: Atl. 30, Tangier B. 



Distribution. Lofuten I. 200 fms. (G. O. Sars), New England 

 (Ferriir). 



Fossil. Pliocene : Coralline Crag. 



Both the ' Porcupine ' specimens are imperfect ; but they agree 

 with Crag specimens in every respect (especially in being tricarinated) 

 except in being spirally and rather strongly striated. A. tricarinatus 

 of Searles Wood is certainly another variety, as he suspected. The 

 spiral striae are wanting in 5Jorwegian specimens, but are conspicuous 

 in the umbilicus of Crag specimens. 



The operculum is not known ; and it is therefore questionable 

 whether the present species belongs to Adeorbis or to Homalaxis. 

 It shares some of the characters of both genera. 



2. Adeorbis subcarinatus, Montagu. 

 Helix subcarinata, Mont. Test. Brit. p. 438, t. 7. f. 9. 

 A. subcarinatus, B. C. iv. p. 231, pi. iii. f. 5 ; v. p. 216, 

 pi. ixxix. f. 1. 



'Porcupine' Exp. 1869: St. 18, Lough Swilly. 



Distribution. British and Irish coasts, from Aberdeenshire to 

 Guernsey, Atlantic coasts of France, Spain, and Portugal, through- 

 out the ^lediterranean and Adriatic, and Mogador ; low water to 

 35 fms. The habitat is subliltoral. 



Fossil. Miocene : Bordeaux Basin and Transylvania. Pliocene : 

 Coralline and Bed Crag, Belgian Crag, Central and Southern Italy, 

 Post-tertiary : Portrush and Selsea. 



Several obsolete synonyms. 



The animal and its habits were described by Mr. Duprey in 



