PLATE XIII. 



Fig. 1. — Aviculopecten dissimilis. The left valve, crushed in but fairly whole. 

 From the Limestone of Corrieburn, Scotland. In the Collection of Mr. James 

 Neilson. (Page 71.) 



Figs. 2 and 3. — Aviculopecten dissimilis. The right and left valves of a shell 

 from the Lower Limestone series, Beith. Same Collection. (Page 70.) 



Fig. 4. — Aviculopecten dissimilis. A left valve, the specimen figured as A. 

 ccelatus by M'Coy. In the Woodwardian Museum, Cambridge. (Page 70.) 



Fig. 5. — Aviculopecten dissimilis. A right valve. The type figured by Phillips. 

 Preserved in the Gilbertson Collection, Natural History Museum, South Kensington. 

 (Page 72.) 



Fig. 6. — Aviculopecten dissimilis. The left valve of young specimen from the 

 Carboniferous Limestone of Llangollen. In the Collection of the Geological 

 Survey, Jermyn Street. (Page 70.) 



Fig. 7 .—Aviculopecten dissimilis. The right valve of a young specimen. From 

 the Carboniferous Limestone of Halkin Mountain, Holywell. Same Collection. 

 (Page 70.) 



Fig. 8. — Aviculopecten dissimilis. Showing the ears of the right valve. From 

 Glen Hind Og, Dairy. My Collection. (Page 70.) 



Fig. 9. — Aviculopecten semicostatus. The internal cast of a left valve. The 

 type of Portlock's Pecten semicostatus. Preserved in the Collection of the Geolo- 

 gical Survey, Jermyn Street. (Page 69.) 



Fig. 10. — Aviculopecten semicostatus. The specimen figured by Phillips as 

 Pecten plicatus, Sow. In the Gilbertson Collection, Natural History Museum, 

 South Kensington. (Page 70.) 



Fig. 11. — Aviculopecten semicostatus. A cast showing the hinge-plate. From the 

 Carboniferous Limestone of Poolvash, Isle of Man. In the Collection of Mr. R. 

 Law. (Page 70.) 



Fig. 12. — Aviculopecten semicostatus. A right valve. From the Carboniferous 

 Limestone series of Redesdale. My Collection. (Page 09.) 



Fig. 13. — Aviculopecten semicostatus. A left valve, showing the posterior ear. 

 Redesdale Ironstone Beds, Redesdale. My Collection. (Page 09.) 



Fig. 14. — Aviculopecten semicostatus. The type of A. docens, M'Coy. The cast 

 of a left valve. From Lowick. In the Woodwardian Museum, Cambridge. 

 (Page 7<».) 



Fig. 15 — Aviculopecten semicostatus. A right valve. From the Redesdale Iron- 

 stone. My Collection. (Page 69.) 



