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276 
1. A ventral view, natural size. 
2-4. Dorsal, ventral and profile views of a specimen of the prevailing form; enlarged to two 
diameters. 
5. Dorsal view of an individual of an elongate form, in which the sinus of the dorsal valve 
is more strongly marked than usual (enlarged). 
6. A still further enlargement of the rostral portion of fig. 2, for the purpose of showing delti- 
dial plates, foramen, etc. (The lithographer has unfortunately omitted the lines marking 
the limits of the deltidial plates.) 
PLATE 45. 
Rhynchospira lepida.. 
Figs. 7-15. Trematospira gibbosa. 272 
7, 8. Dorsal and ventral views of a small specimen. 
9. Dorsal view of a specimen of medium size. 
10-14. Dorsal, ventral, cardinal, profile and front views of a full grown individual. 
15. Enlargement of the cardinal portion of a dorsal valve of this species, showing the peculiar 
cardinal process and slender mesial septum. 
Figs. 16-32. Trematospira hirsuta. 274 
16. A dorsal view of an individual,' from the Corniferous limestone of Louisville, Ky. 
17 -19. Dorsal views of specimens, showing variations in size and development of the mesial 
fold and sinus; fig. 19 being essentially destitute of these features. 
20. Ventral views of a large individual. 
21, 22. Dorsal and profile views of a round and gibbous specimen. 
23-27. Dorsal, ventral, profile, cardinal and front views of a full grown individual. 
28. Interior of a dorsal valve. 
29. An enlargement of the upper part of fig. 28, showing cardinal process, dental sockets, and 
bases of the crura. 
30. Interior of a ventral valve. 
31. Enlargement of the beak of fig. 30, showing the teeth, false area and foramen. 
32. An individual having the greater part of the dorsal valve removed, showing the internal 
spires and bases of the crura. 
Figs. 33-57. Ntjcleospira concinna.. 279 
33. Cast of a ventral valve, from the Schoharie grit. 
34. 35. Dorsal and profile views of a specimen, from the Upper Helderberg limestone. 
36, 37. Dorsal views of small individuals, from the Hamilton group; the latter preserving the 
fine hair-like setae on a part of the shell. 
38, 39. Dorsal and profile views of a specimen where the valves are of nearly equal depth. 
40.41. Dorsal views of flattened specimens which preserve the fine setae very beautifully. 
42-46. Dorsal, ventral, profile, cardinal and front views of a large and well preserved speci¬ 
men where the valves are of unequal depth.' 
47, 48. Interior and profile views of a dorsal valve, showing the size and form of the cardinal 
process. * 
49.. Enlargement of the cardinal process, showing the small elevated pad for the attachment of 
the cardinal muscles, the dental sockets, and the points for the attachment of the crura. 
50. Interior of a ventral valve. 
51. Enlargement of the beak of the ventral valve, showing the teeth and false area. 
52. View of a specimen showing the spires. 
53. 57. The internal cast of a dorsal and a ventral valve; enlarged to two diameters. 
54. The cast of a ventral valve of the natural size. 
55. 56. The casts of dorsal valves, of the natural size, showing some variation in the form and 
markings. 
58. Enlargement of the surface, showing the fine set®, and the bases of others which have 
been broken away, giying a minutely pustulose surface. It is this feature which 
gives the apparent punctate texture to the surface of these shells. 
