PLATE XVIII. 



Fig. 1. — Ctenodonta sinuosa. A cast of the right valve, showing muscle-scars, hinge-teeth, aud 

 pallial line, from a marine band below the Third Millstone-grit, Congleton Edge, Cheshire. My 

 Collection. (Page 210.) 



Fig. 1 a. — Ctenodonta sinuosa. The hinge- plate of the same specimen enlarged. 



Fig. 2. — Ctenodonta sinuosa. A perfect cast, showing hinge-plate. Same locality and collection. 

 (Page 210.) 



Fig. 3. — Ctenodonta sinuosa. A testiferous example. Same locality and collection. (Page 210.) 



Fig. 4. — Ctenodonta sinuosa. A younger example, with 4 a, the upper surface showing the narrow 

 escutcheon. Same locality and collection. (Page 210.) 



Figs. 5, 6. — Ctenodonta sinuosa. Two young specimens to show the truncate, obtuse posterior 

 end in this stage of existence. Same locality and collection. (Page 210.) 



Fig. 7. — Protoschizodus impressus. A testiferous left valve from the Upper Limestone series of 

 Orchard, near Glasgow. In the Collection of Mr. J. jNeilson. (Page 233.) 



Fig. 8. — Protoschizodus impressus. A perfect cast from one of the Lowick Limestones, showing 

 muscle-scars and pallial line. In the Woodwardian Museum, Cambridge. "With fig. S a, a view 

 from above. (Page 233.) 



Fig. 9. — Protoschizodus impressus. A smaller cast. Same locality and collection. (Page 233.) 



Fig. 10. — Protoschizodus obliquus. A decorticated specimen from the Lower Limestone of 

 Beith. 10 a. — View from above. My Collection. (Page 235.) 



Fig. 11. — Protoschizodus triangularis. A fairly perfect cast from the Lower Limestone series of 

 Beith. My Collection. (Page 242.) 



Figs. 12, 13. — Protoschizodus triangularis. Two casts from the same locality. My Collection. 

 (Page 242.) 



Fig. 14. — Protoschizodus trigonalis. An almost perfect specimen from the upper beds of the 

 Carboniferous Limestone, Castleton, Derbyshire. With 14 a, a view from above. My Collection. 

 (Page 238.) 



Fig. 15. — Protoschizodus subxqualis. A right valve from the upper beds of the Carboniferous 

 Limestone, Hill Bolton, Torks. My Collection. (Page 239.) 



Figs. 16 — 19. — Protoschizodus subxqualis. A sei'ies of specimens from the Carboniferous 

 Limestone of Thorpe Cloud, Derbyshire. These appear much too flat in the drawing. They are 

 very gibbose, with a much compressed and depressed posterior superior wing. My Collection. 

 (Page 239.) 



Fig. 20. — Protoschizodus rectangularis. From the Carboniferous Limestone of Settle. Burrow 

 Collection of the Woodwardian Museum, Cambridge. This specimen is much too flat in the drawing. 

 (Page 237.) 



Fig. 21. — Protoschizodus orbicularis. — A full-sized example of a left valve from the marine band 

 below the Third Grit, Congleton Edge. My Collection. (Page 241.) 



Fig. 22. — Protoschizodus orbicularis. The cast of a left valve, showing muscle-scars, pallial line, 

 and the impression of the hinge-teeth. Same locality. My Collection. (Page 241.) 



Fig. 23. — Protoschizodus orbicularis. A small specimen of the left valve. Same locality and 

 collection. (Page 241.) 



Figs. 24, 25. — Schizodus antiquus. Two imperfect casts of the left valve, showing the pallial 

 line and muscle-scars from bed of a calcareous sandstone below the Millstone grits, Pule Hill, 

 Marsden. My Collection. (Page 225.) 



Fig. 26. — Schizodus antiquus. A small testiferous example from the roof of the Bay Coal, 

 Longton. Collection of Mr. J. Ward. (Page 224.) 



Fig. 27. — Schizodus antiquus. A fine specimen of both valves from the shales below the grits of 

 Pule Hill, Marsden. Collection of Mr. W. F. Holroyd. (Page 224.) 



