PLATE III. 



Fig. 1. — Carbonicola acuta. The original specimen, figured in vol. i, pi. xxxiii, 

 fig. 6, in Sowerby's ' Mineral Conchology.' In the Sowerby Collection, Nat. 

 Hist. Museum, South Kensington. (Page 50.) 



Fig. 2. — Carbonicola acuta ? Ditto, pi. xxxiii, fig. 5 ; but it is a question 

 whether this shell should not rather be referred to C. subconstricta. (Page 53.) 



Fig. 3. — Carbonicola acuta? From the original specimen figured, vol. i, 

 pi. xxxiii, fig. 7, in Sowerby's ' Mineral Conchology.' In the Sowerby Collection 

 of the Nat. Hist. Museum, South Kensington. (Page 54.) 



Figs. 4 — 12. — Carbonicola acuta. A series from the roof of the Cockshead 

 Coal Seam, Adderley Green, North Staffordshire, to show the variation in form 

 and the gradual passage into C. acuta, var. rhomboidalis. My Collection. 

 (Page 50.) 



Figs. 5 a and 11a. — Carbonicola acuta. Figs. 5 and 11 viewed from above, 

 showing the lunule, the external ligament, and the bevelled edges of the hinge- 

 plates posteriorly. (Page 50.) 



Figs. 13 — 21. — Carbonicola acuta, var. rhomboidalis. From the roof of the 

 Cockshead Coal, Adderley Green, North Staffordshire, all showing erosion of the 

 umbones, an obliquity in the lines of growth to the long axis of the shell, and a 

 marked broad, shallow, oblique constriction on the surface of the valve. My 

 Collection. (Page 55.) 



