PLATE XXXVII. 



Page. 



Figs. 1 and '2. Endodbsma orthonotum Meek and Worthen, sp '527 



Lateral and dorsal views of tlie 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. Endodbbma gesnbbi 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. Endodbsma postlattjm:, n. sp 527 



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

 Geol. Survey Museum Eeg. TSo. 8345. 



Figs. 7 to 11. OrTHODESMA CANALICULATUM, n' sp 520 



7 and 8. The right side and a dorsal view of a nearly entire cast. Waynesville, Ohio. 



9. Well preserved but Incomplete cast, showing the anterior end and obscure rays 

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



10. Posterior two- thirds of a cast from the Hudson Eiver 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. 



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



and the cardinal depression. 



Figs. 12 to 14. Orthodbsma minnesotbnsb Ulrich 517 



12. The left side of the type specimen. 



13. Dorsal- view of same. 



14. Anterior part of a dorsal view, x 4. Middle third of the Trenton shales, Minne- 



apolis, Minnesota. 



Figs. 15 and 16. Modiolopsis coitcentkica Hall and Whitfield 510 



15. Exterior of the shell as obtained from a gutta-percha Impression of a natural 



mold. 



16. Finely preserved cast of the interior. In offering these figures I 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. Vanuxbmia sabdesoki Ulrich 555 



(See also plate xxxviii, 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. Ko. 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 PLANODOKSATA Ulrich 589 



(See also plate xlii, figs. 38 to 40.) 



25. Posterior view of the original type. 



26. Eight 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 compbessa Ulrich 600 



(See also plate xlh, figs. 88 to 90.) 



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 valve upon which this species was founded, magnified twice 

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

 Minnesota. 



Figs. 32 and 33. Clidophoeus ? consuetus Ulrich ■_ qqq 



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

 Wykoff, Minnesota. 



Fig. 34. Teohnophoeus BXTENUATUS Ulrich 614 



View of the left side of the cast of the interior upon whicii the species' was 

 fouqded. Middle tbird of the Trenton shales, Minneapolis, Minnesota. 



