PLATE XXXVII. 
SILURIAN SPECIES. 
Fic 
ap Orthis plicata, Sow. After the original figure im ‘Silurian System,’ pl. xxi, 
fig. 6. 
2 » virgata, Sow. Iad., pl. xx, fig. 15. 
3—7. ,, ? spiriferoides, M‘Coy. 3. Caradoc; Llanfyllin. Mus. Geol. Survey. 
4. Internal cast of ventral valve; a, a little projection due 
to the tube. Same locality. 4a. Interior of the same 
valve, taken from the cast by the means of gutta-percha. 
5. Internal cast, in which the cast of the tube is preserved; 
from Bala Limestone, 14 mile east of Bala. Sharpe’s Coll., 
Mus. Geol. Soc. 6. Internal cast of dorsal valve, enlarged. 
Bala Limestone ; Garnedd Quarry, near Bala. 7. Interior 
of dorsal valve, taken with gutta-percha from an internal 
cast. Llanfyllin. 
8—15. ,  ~nsularis, Kichwald. 8, 14. Caradoc; Chair of Kildare. Mus. Geol. 
Survey. 9. A large specimen. Portrane. Mus. Geol. 
Survey, Ireland. 10,11. Llandovery beds ; Mandinam, 
Llandovery. 12,13. Caradoc; Chair of Kildare. 15. In- 
ternal cast of dorsal valve, enlarged. Lower Llandovery ; 
River Sevin, Llellyrhyddod, Llandovery. 
16—22. »  unguis, Sow. 16. Complete form, taken from external cast by means of 
gutta-percha. Caradoc; Gretton. 17. Caradoc; Acton 
Scott. 17a. Enlarged. 18. Caradoc; Cheney Longville. 
18 a. Enlarged. Both in Mus. Geol. Survey. 19. Internal 
cast of dorsal valve, enlarged. From Caradoc ; Gretton. 
Coll. of Mr. Lightbody. 20. Internal cast of ventral valve. 
Caradoc; Horderley. An enlarged figure of Murchison’s 
original specimen, figured in ‘ Silurian System.’ 20a. In- ‘\ 
terior, taken from the cast with gutta-percha and enlarged. 
Mus. Geol. Soc. 
23—26. Strophomena Jukesii, Dav. Caradoc; Grangegeeth, County Meath. Mus. 
Geol. Survey of Ireland. 23. Exterior of ventral valve. 
24. Specimen showing part of internal cast of ventral valve. 
25. Internal cast of ventral valve, much enlarged. 26. Interior 
of same valve, taken from the internal cast with gutta-percha. 
