EXPLANATION OF PLATES. 451 
FIGURE, PAGE, 
6. Spirifer (Syringothyris) typa, Winchell. Carb.; N 
Am. Section through the beak of the ventral valve. 
1. dental plates or lamellze; ¢. tube incomplete; 7, 
mesial ridge, : ; : : : : : . 321 
7. Athyris lamellosa, Ler. }. Carb.; N. America, Eur., 322 
8, 9. Athyris Roissyi, 5 : ; : : : . 322 
10-12. Kayseria lens, Phil. Devonian; Eifel, . : » 822 
13. Bifida lepida, Goldfuss. Devonian; Europe, ; . 324 
14. Merista (Whitfieldia) tumida, Dalm.  Silur. ; Eng., . 324 
15. Hindella umbonata, Billings. Paleozoic; N. Amer.,. 326 
PLATE 138: 
16-18. Nucleospira ventricosa, Hall. L. Helderb. 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; ¢, ¢, erural 
processes; 6, b, dental pockets; 7, muscular impres- 
sions; s, medio-longitudinal septum ; ¢,¢, teeth; 2, a 
flattened space or false area beneath the beak (Hall), 323 
19. Merista herculea, Desl. U. Silurian; Bohemia, . . 323 
90. Merista (Meristella) tamida, Dalm. U, Sil.; Gotland, 324 
21-93. Retzia trigonella, Schloth. Muschelkalk ; Venice, 324 
94-97. Retzia (Trematospira) hirsuta, Hall. Dev. ; Ky., 325 
98,29. Dayia navicula, Sowb. Ludlow Shales ; Shropshire, 
England, . : 5 : : : : : . o20 
30. Acambona prima,White. Burl. Limest.; Burlington, Ia., 325 
3, Pd Uncites gryphus, Schloth. Devonian; Bensberg, . 326 
33-36. Koninckia Leonhardi, Wissm. Trias; St. Cassian, 
Tyrol, : ; é : : ; : : Be i 
37-39. Orthis striatula, Schloth. Devonian; Hifel, . . 328 
40. Orthis (Platystrophia, lynx, Eichw.  L. Silur. ; Cinn., 
Ohtoye : : : ; : : > : . 328 
41, 42. Orthisina anomala, Schloth. L. Silur.; Russia, . 329 
43, 44. Tropidoleptus carinata, Conr. Hamilton Gr. ; N:Y., a0 
45-48. Vitulina pustulosa, Hall. Hamilton Gr.; N.Y., - 330 
49,50. Strophomena alternata, Conr. L. Sil.; Cinn., O., 330 
51,52. Strophomena (Leptagonia) rhomboidalis, Dalm. 
U. Silurian ; Gotland, : ; ; : : . 331 
53. Strophomena (Leptena) transversalis, Dalm. Upper 
Silurian; Gotland, : : . 
PLATE 139. 
54,55. Strophomena (Leptena) transversalis, Dalm. U. 
Silurian; Gotland, . ; : i ; ; . 331 
56,57. Davidsonia Verneuili, Bouchard. Devon. ; Hifel, . 331 
58. Porambonites equirostris, Schloth. L. Silur.; Russia, 332 
