636 



SHELLS OF THE LOWER SILURIAN ROCKS. 



This species occurs in clusters in the Caradoc Sandstone. 

 Loc. Soudley, near Acton Scott, east flank of Caer Caradoc. 

 Orbicula granulata, PL 20. f. 5. Lenticular, punctated. 



This is an imperfect specimen, but from its remains we presume that it was very flat, with 

 the apex near the margin. Diameter about | an inch. 

 Loc. Chatwall, east flank of the Caradoc. 

 Leptcena sericea, PI. 19. f. 1. (L. striatella ? Balm. It c. p. 111. t. i. f. 5.) Semicircular; finely 

 striated longitudinally, with a silky lustre ; a few striae deeper than the others ; larger valve 

 convex, the other nearly flat ; front not concave, considerably deflected at the edge. Length 

 5 lines, width 10 lines. 



In general form this fossil resembles L. lata of the Ludlow Rock (PI. 5. f. 13.), but has 

 much finer stria? and more angular sides ; the front also is straighter, and there are no indica- 

 tions of spines. Sometimes a few concentric lines of growth are conspicuous. 

 Loc. Whittingslow ; Horderley, and east flank of Caradoc 1 ; Guils field and Cefn, near Welch- 

 pool; the Maen and Allt-yr-ankr, Meifod ; east flank of Berwyns ; Goleugoed ; and 

 Cerrig-gwynion, Llandovery. 

 Leptcena sericea, var., PI. 19. f. 2. Rather longer than the last. 



Loc. Cefn-rhyddan, Llandovery. 

 Leptcena complanata, PI. 20. f. 6. Semioval, nearly as long as wide, almost flat, finely radiated; 

 radii linear, increasing in number towards the deflected margin ; beak projecting ; the ex- 

 tremities of the hinge line rounded. Length 11 lines, width 1 inch, one imperfect specimen 

 is larger. 



Loc. Acton Burnell, Salop. 

 Leptcena duplicata, PI. 22. f. 2. Transverse, convex, internally marked with furrows arranged in 

 pairs. Length 5|- lines, width 9 lines. 



Loc. Cefn, near Welchpool ; Robeston Wathen, Pembrokeshire. 

 Leptcena euglypha, PI. 12. f. 1. Wenlock Limestone. 



Loc. Horderley ; and Cefn, near Welchpool. 

 Leptcena depressa, PI. 12. f. 2. Occurs from the Aymestry Limestone downwards through the 



inferior strata. 



Loc. Hope Mill, Shelve ; Goleugoed, Mandinam, Caermarthenshire. 

 Leptcena tenuistriata, PI. 22. f. 2 a. Semicylindrical, closely striated; top of the upper valve with 

 12 or more concentric rugae, convex; sides expanded. 



A shell much resembling L. depressa, and about the same size, but ornamented with much 

 closer striae and of a thinner substance. Can this be L. depressa of Swedish authors, and may 

 our L. depressa be their L. rugosa ? 



Loc. Marloes Bay ; Narbeth, Pembrokeshire ; also at Gaerfawr in the Caradoc Sandstone 

 of Montgomeryshire. 



Atrypa crassa, PI. 21. f. 1. Spherical, smooth ? very thick, the three muscular impressions very 

 deep, the central one tongue-shaped, striated, the lateral ones marked with 5 — 7 angular furrows 

 more or less deep. 



r Whenever the reference " east flank of Caradoc " is given, the fossils alluded to, may be detected at Soudley 

 Quarries near Hope Bowdler, "Wilson, Enchmarsh, Broome, Chatwall, and in the hills ranging to Acton 

 Burnell and Stevens Hill on the north-east, and to Acton Scott, Whittingslow, Horderley, Long-Lane, Wis- 

 tanstow, Cheney Longville, Aston and Corton on the south-west. 



