PLATE XII. 



Fig. 1. — Aviculopecten tabulatus. A left valve, presumably M'Coy's type of 

 the species. From Derbyshire. In the Woodwardian Collection, Cambridge. 

 (Page 68.) 



Fig. 2. — Aviculopecten tabulatus. A right valve. From Park Hill. In the 

 Collection of the Geological Survey, Jermyn Street. (Page 68.) 



Fig. 3.— Aviculopecten tabulatus. A left valve. From Hill Bolton, Yorkshire. 

 My Collection. (Page 68.) 



Fig. 4. — Aviculopecten tabulatus. The impression of a right valve, showing the 

 large posterior ear. From Poolvash, Isle of Man. In the Collection of Mr. R. Law. 

 (Page 67.) 



Fig. 5. — Aviculopecten plicatus. A right valve. From the Carboniferous Lime- 

 stone of Ireland. In the Woodwardian Museum, Cambridge. (Page 73.) 



Fig. 6. — Aviculopecten plicatus. The left valve. The type of Sowerby's Peeten 

 plicatus. Preserved in the Sowerby Collection, Natural History Museum, South 

 Kensington. (Page 74.) 



Fig. 7. — Aviculopecten EsJcdalensis. — A young bivalved example. From the 

 Calciferous Sandstone series, River Esk, Glencartholm. In the Collection of the 

 Geological Survey of Scotland. (Page 74.) 



Fig. 8. — Aviculopecten plicatus. A right valve. From the Limestone of 

 Rathkeale, co. Limerick. In the Collection of Mr. J. Wright. (Page 74.) 



Fig. 9. — Aviculopecten plicatus. A left valve, from the Limestone of 

 co. Dublin, showing the ribs to be crenulated. Same Collection. (Page 73.) 



Fig. 10. -^-Aviculopecten Eskdalensis. Right and left valves. Calciferous Sand- 

 stone series, River Esk. (Page 75.) 



Fig. 11. — Aviculopecten EsJcdalensis. Right and left valves, with rather coarser 

 ribs. Same locality and Collection. (Page 74.) 



Fig. 12. — Aviculopecten fimbriatus. The cast of a left valve, with a small 

 portion of the last preserved, showing the ornament. From Castleton. My 

 Collection. (Page 93.) 



Fig. lo. — Aviculopecten fimbriatus. A right valve. In the Collection of the 

 York Museum. From Settle. (Page 93.) 



