PLATE XI. 



Fig. 1. — Parallelodon tenuistria. A testiferous example. From the Carboniferous Limestone 

 of eo. Meath. In the Collection of the Geological Survey of Ireland, Dublin. (Page 151.) 



Fig. 2. — Parallelodon tenuistria. A cast of the left valve. From the Limestone of Garrahies, 

 co. Kerry. Same Collection. (Page 151.) 



Fig. 3. — Parallelodon tenuistria. A right valve, with portion of the test preserved. Same 

 locality and Collection. (Page 151.) 



Fig. 4. — Parallelodon tenuistria. The type specimen figured by M'Coy, from the Lower 

 Limestone of Cregg, Nobber. From the Griffith Collection of the Museum of Science and Art, 

 Dublin. (Page 151.) 



Fig. 4 a. — Parallelodon tenuistria. The type specimen, viewed from above. 



Fig. 5. — Parallelodon semicostatus. The type specimen figured by M'Coy, from the Calp series of 

 Manor Hamilton. Same Collection. (Page 157.) 



Fig. 6. — Parallelodon semicostatus. A left valve, from the Shale below the Linn Limestone of 

 Linn Spout, Dairy. My Collection. (Page 157.) 



Figs. 7 and 8. — Parallelodon semicostatus. Two right valves, showing variations iu shape. Same 

 locality. My Collection. (Page 157.) 



Fig. 9. — Parallelodon semicostatus. A left valve, of a less transversely produced form. Same 

 locality. My Collection. (Page 157.) 



Fig. 10. — Parallelodon semicostatus. The cast of a left valve, which shows some details of the 

 hinge, but these are too deep in the hollow behind the umbo to be shown in the drawing. Same 

 locality and Collection. (P;ige 157.) 



Fig. 11. — Parallelodon theciformis. A well-preserved left valve, from the Carboniferous 

 Limestone of Settle. In the Burrow Collection of the Woodwardiau Museum, Cambridge. 

 (Page 171.) 



Fig. 12. — Parallelodon theciformis. A large example of the right valve, from the Carboniferous 

 Limestone of Thorpe Cloud, Derbyshire. My Collection. (Page 171.) 



Figs. 13 — -16. — Parallelodon theciformis. A series of examples, from the Carboniferous Lime- 

 stone of Settle, Yorkshire. In the Burrow Collection of the Woodwardiau Museum, Cambridge. 

 (Page 171.) 



Figs. 17 — 20. — Parallelodon Geinitzi. A series of left valves, from the Shale below the Limestone 

 of Linn Spout, Dairy. My Collection. (Page 1G9.) 



Fig. 21. — Parallelodon Geinitzi. A right valve of a transversely elongated specimen. Same 

 locality. My Collection. (Page 169.) 



Fig. 22. — Parallelodon decussatus. A left valve. The original shell, figured by M'Coy, from the 

 Lower Limestone, Little Island, Cork. In the Griffith Collection of the Museum of Science and 

 Art, Dublin. (Page 159.) 



Fig. 23. — Parallelodon fallax. A right valve, from the Carboniferous Limestone of Settle. In 

 the Burrow Collection of the Woodwardian Museum, Cambridge. (Page 161.) 



Fig. 24. — Parallelodon fallax. The cast of a left valve, showing the anterior and posterior hinge- 

 teeth, adductor muscle-scars, and pallial line, from the Carboniferous Limestone of Narrowdale, 

 Staffordshire. In the Collection of the Geological Survey, Jermyn Street. (Page 181.) 



Figs. 25, 26. — Parallelodon fallax. Two very perfect examples, from the Carboniferous Limestone 

 of Settle, Yorkshire. In the Burrow Collection of the Woodwardian Museum, Cambridge. (Page 161.) 



Fig. 25 a. — Parallelodon fallax. Fig. 25 viewed from above. 



Fig. 27. — Parallelodon fallax. A left valve, from the Carboniferous Limestone of Hill Bolton, 

 Yorkshire. My Collection. (Page 161.) 



Fig. 27 a. — Parallelodon fallax. The same example, showing the hinge-line. 



Fig. 27 b. — Parallelodon fallax. The same example viewed from above, showing the area. 



Fig. 28. — Parallelodon Haimeanus. A cast, showing the hinge and adductor muscle-scars. From 

 the Carboniferous Limestone at the entrance to the Odin Mine, Castleton. My Collection. (Page 163.) 



Fig. 28 a. — A magnified view of the posterior hinge-teeth of Fig. 28. 



Fig. 29. — Parallelodon Haimeanus. A testiferous right valve, from the Carboniferous Limestone 

 of Trey Cliff, Castleton. In the Collection of the Geological Survey Museum. (Page 163.) 



Fig. 30. — Parallelodon Haimeanus. A fine example of left valve, from the same locality. My 

 Collection. (Page 163.) 



Fig. 30 a. — Parallelodon Haimeanus. A portion of the test magnified, showing the fine lines of 

 growth between the more marked concentric transverse striations. 



Fig. 31. — Parallelodon Haimeanus. The cast of a left valve, from the Carboniferous Limestone of 

 Narrowdale, Staffordshire. In the Collection of the Geological Survey, Jermyn Street. (Page 163.) 



