Plants^ Geology, 



275 



a single visit ; and the following list of organic remains is the 

 result of that day's labour : — 



Conchifera bimusculbsa : Conchacea fluviatUia ; Cyclas ob- 

 licjua, cornea, and pusilla ; Cyrena trigonula ITVood^, Naiada : 

 Anodonta sp. ? ; U^nio sp. ? Trachelipoda : Colimacea ; Suc- 

 cinea amphibia and oblonga ; Helix hortensis, lucida, fusca, 

 rufescens, and palud5sa {Montagu); Carychium minimum, 

 Pupa marginata, Bulimus lubricus. Lymnceana: Lymnse'a 

 auricularia, peregra, fossaria, and palustris; Planorbis cari- 

 natus, corneus, vortex, contortus, imbricatus. Peristomidna : 

 Paludina impura, Valvata piscinalis and cristata. Crustacea : 

 Branchiopoda ; one Cypris. Some fragments of bones, and 

 the lower jaw of one of the gnawers, a species of Arvicola. 



Cyrena trigonula [Wood]. — The accompanying shell {fig, 

 45. fir, h) is very abundant at Stutton. I have ventured to name it 



b 



trig6nula until some more appropriate epithet be given to it. 

 The shell may be thus characterised : — Testa ovato-trigona, 

 subaequilatera, crassa, subimbricata, dentibus cardinalibus 

 tribus in utraque valva, dentibus lateralibus magnis serratis. 

 It approaches near to C trigona of Deshayes, Paris Foss, 

 pi. 19. fig. 16, 17.; from which, however, it is easily distin- 

 guished, by its being nearly equilateral and subimbricated. 

 The generality of the specimens are much eroded externally ; 

 but one or two which I have distinctly show the depressed 

 imbrications. 



All the other species of shells I have been able to identify 

 with recent analogues ; the ITnio and Anodonta are scarcely 

 perfect enough to decide upon. I have received a ^qw spe- 

 cimens of the Valvata piscinalis, from a freshwater formation 

 at Copford, about five miles west of Colchester. But this is 

 a spot I have not yet visited : perhaps some correspondent in 

 that neighbourhood may make us better acquainted with its 

 contents. — S. V. Wood. Woodbridge, March 27. 1834. 



[Mr. J. D. C. Sowerby has drawn the figures a and b 

 from some of the specimens obligingly forwarded by Mr. 

 Wood. Mr. Sowerby remarked that the Cyrena trigonula 

 Wood assimilates closely to the Cyrena deperdita Sowerby in 

 Mineral Conchology, fig. 162. and our.y^. 45. c, but differs 

 from it in its posterior side being less angular, and in its newer 

 geological position.] 



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