PLATE 26 



Figs. Barrandella linguifera (Sowerby) 



1,3,5,6. — Dorsal, ventral, posterior, and lateral views of 

 a complete individual. 

 Silurian (Gotlandian), Gotland, Sweden. Cat. No. 

 8 1680. xl. 



Figs. Gypidula multicostata Dunbar 



18. — Ventral interior, showing spondylium greatly thick- 

 ened by growth of adventitious shell. 

 Devonian (Birdsong), Birdsong Creek, Camden 

 Road, Tenn. Cat. No. S 1 764. x 1. 



Barrandella sp. 



2, 7. — Dorsal and posterior views of an internal mold, 

 showing septa. 

 Silurian (Brassfield), Eaton, Ohio. Cat. No. 

 S1674. xl. 



Gypidula acutilobata procerula (Barrande) 



22, 23, 27. — Lateral, ventral, and dorsal views, showing 

 exterior. 

 Devonian (Ff,), Koniepruss, Bohemia. Cat. No. 

 S1803. xl." 



Pentamerella cf. arata (Conrad) 



4. — Dorsal interior, showing long plates of dorsal valve 



which carry brachial processes. 

 17. — Ventral interior, showing spondylium. Septum very 

 short. 

 Devonian (Onondaga), Falls of the Ohio, Louis- 

 ville, Ky. Cat. No. S 1731. x 1.5. 

 13. — Ventral interior, showing short spondylium and two 

 pallial trunks. 

 Devonian, Moreland, Ky. Cat. No. S 1726. x 1. 



Pentamerella arata (Conrad) 



20. — Dorsal view of internal mold, showing septa. 



Devonian (Schoharie grit), Schoharie, N. Y. Cat. 

 No. S 1735. xl. 



Pentamerella fultonensis Branson 



14-16. — Ventral, dorsal, and lateral views of exterior. 



Devonian (Callaway Is.), Auxvasse church, Calla- 

 way Co., Missouri. Cat. No. S 1724. x 1. 



Gypidula dudleyensis Schuchert 



24, 28, 34, 37. — Dorsal, ventral, lateral, and posterior 

 views, showing external form and ornamentation. 

 Silurian (Wenlock), Dudley, England. Cat. No. 

 S1789. xl. 



Gypidula coeymanensis Schuchert 



26, 29. — Posterior and dorsal views of exterior, x 1 . 

 31,35. — Interior, showing spondylium, median septum, 



and brachial processes in place, x 1.5. 

 32. — Dorsal interior, showing plates, x 1.5. 

 40. — Both valves in conjunction. The spondylium and 

 its relation to the dorsal plates are clear, and the nature 

 of the septum is visible, x 1.5. 

 Devonian (Helderberg, Coeymans), Clarksville, 

 Albany Co., N. Y. Cat. Nos. S 1697 (figs. 31,35), 

 S 1792 (figs. 26, 29), and S 1797 (figs. 32, 40). 

 38. — Posterior portion of ventral valve, showing spondylium 

 and median septum. 

 Devonian (Coeymans), Indian Ladder, N. Y. Cat. 

 No. S 1782. X 1. 



Pentamerella cf. pavilionensis (Hall) 



19. — Dorsal interior, showing important lamella:. 



Devonian, Alpine, Mich. Cat. No. S 1736. x 1. 



Clorinda tumidula (Billings) 



8, 1 2. — Dorsal and posterior views, showing characteristic 



exterior. 



9, 10, 11,21 . — Ventral, anterior, dorsal, and lateral views 



of exterior. 

 Silurian (Gun River), Anticosti. Cat. Nos. S 1685, 

 S 1693 (figs. 8, 12). X 1. 



Gypidula romingeri Hall and Clarke 



36, 39. — ^Ventral and dorsal interiors, showing internal 

 plates. Brachial processes broken from dorsal valve. 

 Devonian, Grand Lake, Presque Isle Co., Mich. 

 Cat. No. S 1698. x 1.5. 



Sieberella sieberi (V. Buch) 



25, 30, 33. — Dorsal, lateral, and ventral views of two speci- 

 mens, showing contour and profile of valves. 

 Devonian (Ffj), Koniepruss, Bohemia. Cat. No. 

 S1721. X 1. 



246 



