PLATE XIII. 



Fig. 1. — Parallelodon ornatissimus. A full-grown, decorticated right valve, 

 from the Carboniferous Limestone of Thorpe Cloud. My Collection. (Page 155.) 



Fig. 2. — Parallelodon ornatissimus. A right valve, with portion of the test 

 preserved, showing in front the anterior adductor muscle-scar and pallial line. 

 Same locality. My Collection. (Page 155.) 



Fig. 2 a. — Parallelodon ornatissimus. The same shell viewed from above, 

 showing the large ligamental area. (Page 155.) 



Fig. 2 b. — Parallelodon ornatissimus. An enlarged view of a portion of the 

 ornamentation of the above valve, from the dorsal slope. (Page 155.) 



Fig. 3. — Parallelodon ornatissimus. A right valve, which has been rolled, and 

 the other portion of the test removed. Same locality. My Collection. (Page 155.) 



Fig;. 3 a. — Parallelodon ornatissimus. — The same valve viewed from above, 

 showing the large elongate area, with longitudinal striee. Same locality and 

 Collection. (Page 155.) 



Fig. 4. — Parallelodon ornatissimus. The cast of a young right valve, showing 

 the anterior adductor muscle-scar. Same locality and Collection. (Page 155.) 



Fig. 5. — Parallelodon ornatissimus. A testiferous example of the left valve 

 of a young example, showing the very fine state of the ornament at this stage 

 of growth. Same locality and Collection. (Page 155.) 



Fig. 6. — Parallelodon ornatissimus. — The cast of a left valve. Same locality 

 and Collection. (Page 155.) 



Fig. 7. — Parallelodon obtusus. The hinge showing anterior teeth and area of 

 the specimen figured PL XII, fig. 5. (Page 167.) 



Fig. 8. — Parallelodon Ilaimeanus. A medium-sized right valve from the 

 Carboniferous Limestone of Castleton, in the Collection of Mr. R. Allen. 

 (Page 163.) 



Fig. 9. — Parallelodon meridionialis, de Koninck. The cast of both valves, 

 showing the posterior hinge-teeth, from the Millstone Grit of Sawley, near Ripon. 

 This shell is only doubtfully referred to this species, as it is the only example that 

 I have yet seen from Great Britain, and the species is therefore not described 

 in the text. My Collection. 



Fig. 10. — Parallelodon Oeinitzi. The anterior part of the hinge of a right 

 valve, from the shale below the Linn Limestone, Linn Spout, Dairy. My 

 Collection. (Page 169.) 



Fig. 10 a. — Parallelodon Geinitzi. The same magnified to show details. 

 (Page 169.) 



Fig. 11. — Parallelodon divisus. A left valve, from a band of marine limestone 

 in the Calciferous Limestone series, Randerstone, Fife. My Collection. (Page 172.) 



Fig. 11 a. — Parallelodon divisus. An enlarged view of the same shell. 



Fig. 12. — Parallelodon divisus. The hinge-plate of a left valve. Same 

 locality. My Collection. (Page 172.) 



Fig. 12 a. — Parallelodon divisus. An enlarged view of the hinge-plate. 



Fig. 13. — Parallelodon divisus. An example labelled Modiola divisa in the 

 Griffith Collection, Dublin. (Page 172.) 



Fig. 14. — Parallelodon divisus. An example showing both valves, from the 

 Lower Carboniferous Beds of Eskdale. My Collection. (Page 172.) 



Fig. 15. — Parallelodon semicostatus. A fragment showing the anterior portion 

 of the right hinge-plate. Fig. 15 a. — The same, magnified. My Collection. 

 (Page 157.) 



