PLATE XXIX: 
SILURIAN SPECIES. 
Fig. 
1—10. Orthis polygramma, Sow. 1, 2. The two original specimens figured in 
‘Silurian System.’ Powis Castle Park. Mus. Geol. 
Society. 3. Lower Llandovery; Gorlwyn. Mus. Geol. 
Soc. 4—7. Wenlock Shales ; near the North Esk Reser- 
voir, Pentland Hills. 4 and 5 are in the Mus. Geol. 
Survey. 8, 8a. Internal cast of dorsal valve. 8 4, 8. 
Internal cast of ventral valve. 9. Internal cast of 
ventral valve. 10. Interior of dorsal valve; taken in 
gutta-percha from an internal cast, from the Pentland 
Hills. Mus. Geol. Survey. 
11—13. »  reversa, Salter. 11. Internal cast of dorsal valve; 12, of ventral 
valve. 11 qa@and 12a. Magnified. ‘The original speci- 
men figured in the ‘Synopsis Sil. Foss. of Ireland,’ 
from Egool, Ballaghderra, and Cappacorcogue, Cong. 
Sir R. Griffith’s Coll. 13. Lower Llandovery; Man- 
dinam, near Llandovery. Mus. Geol. Survey. 
14—18. be ne var. Mullochiensis. 14, 15. Llandovery rock; Mulloch 
Quarry, Dalquorhan, Ayrshire. 16, 17. Internal cast 
of both valves. Same locality. 18. Woolhope Lime- 
stone ; Sandbanks, Presteign. Mus. Geol. Survey. 
19—20. ,,  Bailyana, Day. Caradoc beds; Townland of Ballybro, one mile 
north of Tagot, County Wexford. Mus. Geol. Survey 
of Ireland. 19. Internal cast of dorsal valve. 19a. In- 
terior of the same valve, taken from a cast, enlarged. 
20. Internal cast of ventral valve. 20a. Interior of 
ventral valve, taken from a cast, enlarged. 
