PLATE XXXVII. 



PAGE. 



Figs. 1 and 2. ENDODESMA ORTHONOTUM Meek and Worthen, sp 527 



Lateral and dorsal views of the original type of this species. The specimen is a 

 good cast of the interior, in solid limestone, of a left valve. All of it is now 

 exposed, the tough matrix, which covered a considerable portion of the ventral 

 margin when it was used by Meek and Worthen, having been removed before 

 it was redrawn for the present work. Lower Trenton limestone, Dunleith, 

 Illinois. 



Figs. 3 and 4. ENDODESMA GESNERI Billings, sp 528 



Lateral and dorsal views of a good cast of the interior of a right valve. Trenton 

 limestone, Ottawa, Canada. Introduced for comparison with the other species 

 of this proposed genus. 



Figs. 5 and 6. ENDODESMA POSTLATUM, n. sp 527 



Lateral and dorsal views of an internal cast. Upper Galena, Dubuque, Iowa. 

 Geol. Survey Museum Reg. No. 8345. 



Figs. 



7 to 

 7 and 



11. 

 8. 

 9. 



10. 



11. 



Figs. 12 to 14. 

 12. 

 13. 

 14. 



Figs. 15 and 16. 

 15. 



16. 



Middle third of the Trenton shales, Minne- 



517 



510 



ORTHODESMA CANALICUUA.TUM, n. sp 520 



The right side and a dorsal view of a nearly entire cast. Waynesville, Ohio. 

 Well preserved but incomplete cast, showing the anterior end and obscure rays 



across the central half. Upper beds of the Cincinnati group, Waynesville, Ohio. 

 Posterior two-thirds of a cast from the Hudson River group near Spring Valley, 



Minnesota. The length of this specimen was reduced by pressure, and to this 



cause we must ascribe the more crowded arrangement of the radiating lines. 

 View of the broken end of same, showing the natural convexity of the valves 



and the cardinal depression. 



ORTHODESMA MINNESOTENSE Ulrich. 

 The left side of the type specimen. 

 Dorsal view of same. 

 Anterior part of a dorsal view, x 4. 

 apolis, Minnesota. 



MODIOLOPSIS CONCENTRICA Hall and Whitfleld 



Exterior of the shell as obtained from a gutta-percha impression of a natural 

 mold. 



Finely preserved cast of the interior. In offering these figures 1 wish it to be 

 understood that the specimens selected are strictly normal for the species as 

 It occurs in Ohio. Further, that the species is very constant, and that all 

 marked deviations in contour which may be observed in a series of specimens 

 are the result of distortion through pressure. 



Figs. 17 to 19. VANUXEMIA SARDESONI Ulrich 555 



(See also plate xxxvm, fig. 45.) 



Lateral, anterior and cardinal views of the best cast seen. Trenton'limestone, 

 Minneapolis, Minnesota. 



Figs. 20 to 24. MODIOLODON PATULUS, n. sp 521 



20 to 22. The left side and anterior and dorsal views of a cast. Lower or middle Galena, 

 Decorah, Iowa. Geol. Sur. Mus. Reg. No. 8363. 



23. The left side of a cast of the interior from the Trenton at Danville, Kentucky. 



24. A small specimen from the middle Galena of Goodhue county, Minnesota. 



Figs. 25 to 28. CTENODONTA PLANODORSATA Ulrich 589 



(See also plate M.I i. figs. 38 to 40.) 



25. Posterior view of the original type. 



26. Right valve of same, with a small part of the surface magnified. 



27. Profile in a postero-basal view. 



28. Cardinal view of same. Upper part of middle third of Trenton shales, Goodhue 



county, Minnesota. 



Fig. 29. CTENODONTA COMPRESSA Ulrich 600 



(See also plate M.I i. figs. 68 to UO.) 



The original type of the species, x 1.3. Upper part of the middle third of the 

 Trenton shales, Goodhue county, Minnesota. 



Figs. 30 and 31. CTENODONTA LONGA Ulrich 590 



Interior of the right valvo upon which this species \v;is founded, nuigriillrd twice 

 and of the natural size. Middle third of the Trenton shales, Goodhue county, 

 M i n nesota. 



Figs. 32 and 33. CLioopnoRus ? CONSUETUS Ulrich 606 



The type specimen of the natural size and magnified twice. Middle Galena near 

 Wykoff, Minnesota. 



Fig. 34. TECHNOPHORUS EXTENUATUS Ulrich 614 



View of the left side of the cast of the interior upon which the species was 

 founded. Middle third of the Trenton shales, Minneapolis, Minnesota. 



