SHELLS OF THE WENLOCK LIMESTONE. 



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angles,, which together with the general form serve to distinguish this shell from Spirifer 

 crenistria of Phillips, to the flatter valve of which some specimens bear a great resemblance. 

 The striae are often so like those on Orthis alternata, PL 19. f. 6., that it is sometimes almost 

 impossible to say to which shell fragments belong. 



Loc. Wenlock ; Dudley ; Aston, near May Hill; Ledbury ; Fownhope ; Abberley ; and near 

 Wigmore. 



Leptcena depressa, Productus depressus passim, f. 2. (Dalm. 1. c. p. 106. t. i. f. 2; His. Pet. Suec. p. 69. 

 t. xx. f. 3 ; Productus depressus, M. C. t. 459.) A shell frequently found on the surface of slabs 

 of limestone at Wenlock and Dudley, and easily distinguished from a somewhat similar fossil 

 which occurs in the Mountain Limestone of the North of England and the Queen's County and 

 other parts of Ireland, and which Prof. Phillips has named Producta analoga. In that shell the 

 valves are almost equally convex, and the deflected portion descends very little lower than the 

 convex surface of the lower valve, while in L. depressa of our Silurian Rocks, the middle of the 

 lower valve is concave, the sides are expanded like wings at the extremities of the hinges, and 

 the deflected margin is at least as- deep as the valve is long. In the P. analoga, the outline 

 approaches nearer to a semicircle than in the L. depressa, and in this respect agrees better with 

 the L. rugosa, Dalm., a species we believe not yet found in England. Besides its difference in 

 form, L. depressa is usually of less size than P. analoga. Length of flat portion about § inch ; 

 width 1| inch; length of deflected portion nearly 1 inch. 



Loc. Wenlock ; Dudley ; near Aymestry ; Abberley ; May Hill ; the Lye near Stourbridge. 



This highly characteristic fossil occurs both in the Aymestry and Wenlock Limestones, but most 

 abundantly in the latter. It is sparingly distributed throughout the other strata of the Silurian 

 Series. 



Atrypa didyma, (Dalm.). (See PI. 6. f. 4.) Also Aymestry Limestone. 

 Loc. Limestone Quarries, Eastnor Park, Ledbury. 



Atrypa tenuistriata, f. 3. (Terebratula obtusa, Linn. Trans., vol. xii. p. 516. t. 28. f. 3, 4.) Trans- 

 versely obovate, gibbose, with the beaks rather prominent, and a narrow elevation in the front ; 

 longitudinally striated; beaks small, close. Length If inch; width the same. 



So nearly is this related to A. oblata, M. C. t. 268., which in some states even shows indi- 

 cations of striae, that it is not easily distinguished, but the position of the beaks affords a strong 

 character. The extent of front which is elevated, varies in different specimens. 

 Loc. Wenlock ; Croft ; Crew's Hill and the Purlieus, (Malvern Hills) ; Lindells and Fownhope, 

 Woolhope. 



Atrypa galeata, f. 4. & PI. 8. f. 10. (Dalm. I. c. p. 130. t. V. f. 4. His. Pet. Suec, p. 16. t. xxii. f. 1.) 

 Obovate, ventricose, longitudinally furrowed, finely wrinkled with lines of growth ; front de- 

 pressed in the middle ; lesser valve convex, the other very deep with a large incurved umbo. 

 Length 14 lines; width the same; depth of each valve \ inch. 



The furrows are chiefly confined to the middle of the shell ; they are irregular, and form 

 several teeth in the edge of the deflected portion. The interior has septa resembling those of 

 Pentamerus ; a section of which is shown in PI. 8. f. 10. 



Loc. Westhope in Wenlock Edge ; near Aymestry, fyc. ; also Lower Ludlow Rock. 

 Atrypa affinis, (M. C.) (See PL 6. f. 5.) Also Aymestry Limestone. 



Loc. May Hill ; Limestone Quarries, Eastnor Park ; Malvern Hills ; Abberley Lodge. 

 Atrypa aspera, f. 5. (Dalm. I. c. p. 128. t. iv. f. 3. His. Pet. Suec. p. 75. t. xxi. f. 12. Ter. asper, Schloth. 



Nach. Petr. 1822. p. 68. t. xviii. f. 3.) Orbicular, with the front slightly truncated ; marked 



A k 2 



