GASTEROPODA. 137 



such a form of aperture to its shell would, when known, be found to have 

 characters sufficiently distinct to entitle it to generic distinction. 



It was considered as differing from Skenea, in the peculiarly sinuated form of 

 its aperture. 



1. Adeorbis striatus. S. Wood. Tab. XV, fig. 7. 



Adeorbis striatds. £. Wood. In An. and Mag. of Nat. Hist. 1842, vol. ix, p. 530, pi. 5, fig. 4, 6. 

 Valvata striata. Phil. En. Moll. Sic. vol. i, p. 147, t. 9, fig. 3, 1836. 



A. Testa depressd, minutd, striata, subdiscoided ; anfractibus tribus, convexis,vel sub- 

 cylindraceis ; spird vix elevatd, umbilico mag no ; aperturd patente ; peritremd superne 

 expansd, in/erne sinuatd. 



Shell depressed, small, and striated ; volutions three or four, nearly horizontal ; 

 rounded or subcylindical flattened above ; spire scarcely elevated, with a deep 

 distinct suture ; umbilicus large and wide ; aperture gaping, peritreme projecting on 

 the upper part, deeply sinuated underneath. 



Diameter, \ of an inch ; altitude, \ the diameter. 



Locality. Cor. Crag, Gedgrave and Sutton. 



This is at present a rare shell. I have not met with more than four or five 

 specimens. The volutions are slightly depressed above, and the upper part of the 

 lip is as nearly as possible at the centre of the preceding volution ; the shell is 

 regularly covered with about 12 — 15 broad and rounded striae ; the umbilicus is 

 large, with the volutions visible beneath, up to the apex, and the shell wholly 

 destitute of carinas. This is probably the same species as M. Philippi's shell, which 

 he considered as a Valvata, in consequence of its association with Cyrena Gem- 

 mallarii. This Cyrena is also found mixed with marine shells in the Coralline 

 Crag, at Gedgrave. I believe our shell, A. striatus, to have no connexion with 

 Valvata, but that all the species I have included in this genus are marine animals. 



2. Adeorbis supra-nitidus. S. Wood. Tab. XV, fig. 5, a—b. 



Adeorbis supua-nitidus. S. Wood. Catalogue 1842. 



A. Testa depressd, minutd, supra-nitidd, laviyatd, politd, carinatd, aliquando trica- 

 rinatd; anfractibus 3 — 4, convexis aid cylindraceis ; prope suturam subcanaliculatis ; 

 umbilico magno, aperto, et rugose striato. 



Shell depressed, small, smooth, glossy, and naked above, with from one to 

 three sharp carinas, the upper one small, often wanting; volutions 3—4, with a 

 depression or subcanal near the suture ; umbilicus large, open, coarsely striated 

 within ; peritreme sharp, slightly interrupted by the body whorl. 



Diameter, £ of an inch ; altitude, ^ the diameter. 



Locality. Cor. Crag, Sutton. 



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