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 striatus. S. Wood. lu An. and Mag. of Nat. Hist. 1842, vol. ix, p. 530, pi. 5, fig. 4, 6. 

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



A. Testa depressd, mintdd, striata, subdiscoided ; avfractihus tribus, convexis, vet sub- 

 cylindraceis ; spird vix elevatd, umbilico magna ; apertiird jjatente ; veritremd superne 

 expansd, inferne sinuatd. 



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

 rounded or subcylindrical 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 carinse. This is 

 probably the same species as M. Philippi's shell, which he considered as a Valvata, in 

 consequence of its association with Cyrena Gemmallarii. This Cyrena is also found 

 mixed ^\'ith 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. 



D^ 



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

 Adeoebis supra-nitidus. S. Wood. Catalogue 1842. 



A. Testd depressd, minutd, supra-nitidd, Icevigatd, politd, carinatd, aliquando tricarinatd ; 

 anfradibus 3 — 4, convexis aut cylindraceis ; prope suturam subcanaliculatis ; umbilico 

 inagno, aperto, et rugose striata. 



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

 sharp carinte, the upper one small, often wanting; volutions 3 — 4, with a depression 

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

 sharp, slightly interrupted by the body whorl. 



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



Locality. Cor. Crag, Sutton. 



18 



