370 DK. WHEELTON HIND ON BEITISH [Aug. 1 899, 



mistaken one for the other. The figure of Ct. Halli ^ has a much 

 greater resemblance, and, indeed, it is possible that the species may- 

 be identical, but in the absence of any specimens of the Spanish shell 

 I have hesitated to refer the Penton shells to that species. They 

 seem to me to be more transverse, more pointed posteriorly, narrower 

 from above downward, and neither in the figure nor in the 

 description of Barrois's shell is any mention made of the angular 

 ridge parallel to the hinge-line which is present in Ct. pentonensis. 

 The dimensions of Ct. Halli, Barrels, are here given for com- 

 parison : — Antero-posteriorly, 32 mm. ; dorso-ventrally, 19 mm. 



EXPLANATION OF PLATE XXV. 



Pig. 1. Cteiwdonta pentonensis. Left valve. Penton Linns ; p. 369. Nat. 



size. 



2. , „ Left valve, full-grown size ; same locality. 



Nat. size. 



3. „ . „ Right valve, medium-sized specimen ; same 



locality. Nat. size. 

 3 «, „ „ Pig. 3 viewed from above, showing the lunule 



and angular dorsal edge. Nat. size. 



4. „ „ The hiuge of a left valve, x2; same locality. 



5. Carbonicola Vintu A left valve, X 3, from Chatterley ; p. 367. 



6. „ „ A left valve, x3, crushed, giving rise to an appear- 



ance resembliug that of Discina or Ancylus ; same 

 locality, 



7. „ „ A left valve, X,3, somewhat crushed, with perfect 



contour ; same locality. 



8. „ „ A slab covered by the periostraca of the shells, X 3, 



from Claxheugh, County Durham. 



9. „ „ Portion of a right valve, X 3 ; same locality. 



10. „ „ The impression of a right valve, X 3 ; same locality. 



11. „ „ An uncrushed right valve, x3; same locality. 

 Figs. 12 & 13. Carbonicola Vinti. Small specimens from the Hamil marl-pit, 



Burslem ; p. 367. 



Fig. 14. Anthracomya calcifera. A right valve, x3," from roadside, Bradwell, 

 in limestone ; p. 365. 



Figs. 15 & 19. Anthracomya calcifera. The casts of left valves, x3, from the 

 same locality. 



Fig. 16. Anthracomya calcifera. A right valve, X 3, from the same locality. 



Figs. 17 & 18. Anthracomya calcifera. A left and right valve, x3, showing 

 the hinge-plate and interior, from Slade Lane, Fallowfield, near Man- 

 chester. 



Fig. 20. Anthracomya calcifera. The left valve of a medium-sized specimen, 

 X3, from Bradwell. 



[In the above plate the outlines of figs. 5-20 show the actual size of the 

 specimens. With the exception of those reproduced in figs. 15, 17, 18, & 19, 

 the specimens are all in my collection. The specimens figured as 15 & 19 are 

 in the possession of Mr. Walcot Gibson, F.G.S., and those figured as 17 & 18 

 belong to Mr. 0. Reader of Manchester.] 



^ Barrois, ' Recherches sur les Terrains anciens des Asturies & de la Gtilice, 

 Mem. Soc. G6ol. Nord, vol. ii (1882) No. 1, p. 339 & pi. xvii, fig. 3. 



