EXPLANATION OF PLATES. 451 



6. Spirifer (Syriiagothyris) typa, Winehell. Carb. ; N. 



Am. Section through the beak of the ventral valve. 



Z. dental, plates or lamellae; <. tube incomplete; ?•, 



mesial ridge, . . . - . ■ • • 321 



1. Athyris lamellosa, Ler. i. Carb. ; N. America, Eur., 322 



8, 9. Athyris Roissyi, . " . . • . • .322 



10-12. Kayseria lens, Phil. Devonian ; Eifel, . . .322 



13. Bifida lepida. Goldfuss. Devonian; Europe, . . 324 



14. Merista (Whitfieldia) tumida, Dalm. Silur. ; Eng., . 324 



15. llindella umbonata, Billings. Paheozoic ; N. Amer., . 326 



Plate 138. 



16-18. Nucleospira ventricosa, Hall. L. H^lderb. Gr. ; N. 

 Y. 16, interior of dorsal valve ; 17, interior of ven- 

 tral valve ; 18^ interior of dorsal,with a portion of ven- 

 tral valve attached ; J, cardinal process ; c, c, crural 

 processes ; b, &, dental pockets ; r, muscular impres- 

 sions ; .';, medio-longitudinal septum ; t, t, teeth ; 2, a 

 flattened space or false area beneath the beak (Hall), 323 



19. Merista herculea, Desl. U.Silurian; Bohemia, . . 323 



20. Merista (Meristella) tumida, Dalm. U. Sil. ; Gotland, 324 

 21-23. Retzia trigonella, Schloth. Muschelkalk ; Venice, 324 

 24-27. Retzia (Trematospira) hirsuta. Hall. Dev. ; Ky., 325 

 28, 29. Dayia navicula, Sowb. Ludlow Shales ; Shropshire, 



Engl'and, 325 



30. Acambonaprima,White. Burl. Limest.; Burlington, la., 325 

 31,32. Uncites gryphus, Schloth. Devonian; Bensberg, . 326 

 33-36. KonincldaLeonhardi, Wissm. Trias; St. Cassian, 



Tyrol. 32t 



37-39. Orthis striatula, Schloth. Devonian ; Eifel, . . 328 

 40. Orthis (Platystrophiaj lynx, Eichw. L. Silur. ; Cinn., 



Ohio, . ■ 328 



41,42. Orthisina anomala, Schloth. L. Silur. ; Russia, . 329 

 43,44. Tropidoleptus cailnata, Conr. Hamilton Gr. ; N.Y., 330 

 45-48. Vitulina pustulosa. Hall. Hamilton Gr. ; N. Y., . 330 

 49,50. Strophomena alternata, Conr. L. Sil. ; Cinn., 0., 330 

 51, 52. Strophomena (Leptagonia) rhomboidalis, Dalm. 



U. Silurian ; Gotland, . . . . • .331 



53. Strophomena (Leptfena) transversal! s, Dalm. Upper 



Silurian ; Gotland, ....... 381 



Plate 139. 



54, 55. Strophomena (Leptsena) transversalis, Dalm. U. 



Silurian; Gotland, ....... 331 



56, 57. Davidsonia Verneuili, Bouchard. Devon. ; Eifel, . 331 

 58. Porambonites aequirostris, Schloth. L. Silur. ; Russia, 332 



