PLATE VI. 



Figs. 1, 2. — Posidonoinya romigata. A right and left valve. From Jameston 

 Burn, Dairy. In the Collection of Mr. J. Smith. (Page 30.) 



Fig. 3.^ — Posidonomya comigata. From near Paisley. In the Collection of the 

 Geological Survey of Scotland. (Page 30.) 



Figs. 4, 5. — Posidonomya corritgata. From Blair No. 9 Pit, W. Dairy. Mr. J. 

 Smith's Collection. (Page 30.) 



Figs. 6 — 9. — Posidonomya nidiata. A series of examples from the Calciferous 

 Sandstone series of Glencartholm, Dumfriesshire. Fig. 7 in the Collection of the 

 Geological Survey of Scotland ; Figs. 6, 8, and 9 in my Collection. (Page 31.) 



Fig. 10. — Posidonomya costata. The type of M'Coy's species. In the Griffith 

 Collection, Museum of Science and Art, Dublin. (Page 32.) 



Fig. 11. — Posidonomya Beclieri. A left valve. From the Carboniferous Lime- 

 stone of Castleton, Derbyshire. My Collection. (Page 27.) 



Fig. 12. — Posidonomya Becheri. A right valve. From Budle, Northimiberland. 

 To show the wrinkled periostracum. My Collection. (Page 27.) 



Fig. 13. — Posidonomya Becheri. A large example from the Culm of Swan- 

 l)ridge, Devon. In the Museum of the Geological Survey, Jermyn Street. 

 (Page 27.) 



Fig. 14. — Posidonomya Becheri. A left valve. From Budle, Xorthumberland. 

 Same Collection. (Page 27.) 



Fig. 15. — Posidonomya Becheri. A right valve, with the normal convexity 

 preserved. From the Culm of Swanbridge, Devon. Same Collection. (Page 27.) 



Figs. 16 — 18. — Posidonomya lamellosa. From the Carboniferous Limestone 

 of Castleton, Derbyshire. My Collection. (Page 34.) 



