PLATE XX. 



SILURIAN SPECIES. 



Fig 



1 — .2. Stricllandinia lirata, Sow. sp. Upper Llandovery ; Howler's Heath, Malvern 

 Hills. 1 A, internal cast of dorsal valve. 1 b and 2, 

 internal casts of ventral valve. Dr. HoU's Collection. 



3. „ „ 3 A. Internal cast of dorsal valve ; 3 b, of ventral valve. 



Howler's Heath. Mus. Geol. Soc. 



4, .5, 6. „ „ Internal casts. Upper Llandovery ; May Hill. 



7. „ „ A dorsal valve of very transverse shape. Woolhope 



limestone ; Woolhope. Mus. Geol. Siirv. 



8. „ „ [Sjnrifer ovafus, M'Coy.) Drawn from the specimen of 



which Prof. M'Coy gives a reduced figui'e in his ' Synop. 

 Sil. Uoss. of Ireland,' pi. iii, fig. 24. From Egool, 

 Ballaghadorreen, County INIayo. Sir R. Giiffith's Col- 

 lection. 



9. „ ,, Interior of ventral valve ; and 



10. „ „ Interior of dorsal valve. These figures have been drawn 



from gutta-percha moulds, made from internal casts 

 found at Howler's Heath. 



11. ,, „ Portion of a beautifully presened internal cast of dorsal 



valve from Howler's Heath. Mus. Geol. Surv. 



12. „ „ Horizontal section, close to the hinge. 



1:3. „ „ An internal cast of a small, exceptionally shaped or mal- 



formed specimen. Erom Upper Llandoverv'; Nash 

 Scar. Mus. Geol. Snrv. 



