642 



SHELLS OF THE LOWER SILURIAN ROCKS. 



aperture was nearly round with an angle at its upper part. Diameter 1 inch 4 lines, height 

 1^ inch. 



Loc. Mandinam, Llandovery, 

 Trochus lenticularis, PI. 19. f. 11. Lenticular, smooth, with a sharp edge ; whorls three, with a 



single line round the inner margin. Diameter l£ inch. 

 A very flat shell, we have only seen the upper surface. 



Loc. Old Storridge Hill, Worcester. 

 Littorina striatella, PI. 19. f. 12. Conical, with a convex base, marked with fine longitudinal lines 



of growth ; whorls 3 or 4, rounded. Height 8 lines, diameter 7 lines. 



Loc. Horderley and Wistantow (Caradoc). 

 Turbo ? Prycece, PI. 21. f. 19. We have only a cast of the interior, composed of one whorl, which 



is angular in the middle. The shell appears to -have been very short with a large aperture 



and narrow deep umbilicus ; the substance thick. Height about If inch, diameter nearly 



2 inches. (Collected by Miss Pryce.) 



Loc. Mandinam, Llandovery . 

 Turritella cancellata, PI. 20. f. 18. Subulate?, longitudinally striated, carinated ; carinas about 



6 to each whorl, unequal, crossed by the numerous striae. Diameter 6i lines. 



Loc. Mandinam, Llandovery ; Hope Mill, Shelve. 

 Buccinum f f us if or me, PI. 20. f. 19. Fusiform, smooth; whorls few, the last with a shoulder near 



the upper edge ; aperture narrow, as long as the spire. Height 4| inches, diameter 1 inch 



11 lines. In Caradoc Sandstone with Atrypa hemisphcerica, PI. 20. f. f. f and fragments of 



the stems of Crinoidal animals. 



Loc. Corton, near Presteign. 

 Orthoceras annulatum, PI. 9. f. 5. Also Wenlock Limestone and Shale. 



Loc. Goleugoed, Llandovery. 

 Orthoceras conicum, PI. 21. f. 21. Conical, smooth ; septa near together ; siphuncle central, large, 



cylindrical. Diameter 1 inch 2 lines. 



(Occurs in Upper Caradoc with Pent am. Icevis.) 



Loc. Michaelwood Chase, Tortworth. 

 Orthoceras app>roximatum, PI. 21. f. 22. Cylindrical for part of its length, conical towards the 



apex, smooth, slightly curved, septa very near together; siphuncle lateral. Diameter f inch. 



Loc. Eastnor Park. 



Orthoceras bisiphonatum, PI. 21. f. 23. Septa very numerous, pierced by two siphuncles, one 

 small, very eccentric, globose (inflated) between the septa, the other large, cylindrical, ex- 

 tending from near the small siphuncle to the edge of the septum. Diameter about 3^ inches. 



Orthocerata with two siphuncles have been observed, but there has always appeared some- 

 thing doubtful about them. See description of Mr. Bright's specimen of O. annulatum. In 

 the present instance, however, this structure cannot be questioned. 

 Loc. Gorllwynfach, Llandovery. 



Nautilus undosus, PI. 22. f. 17- Discoid, inner whorls exposed; sides largely waved; front flat; 

 septa numerous ; aperture oblong. 



This specimen is obliquely compressed into an oval form and much resembles Nautilus 

 compressus (M, C. t. 38.). The large waves on the sides distinguish it. Diameter 3£ inches, 

 length of aperture 10|- lines. 

 Loc. Blaeny-cwm, near Llandovery . 



