PLATE XXIX. 
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(Figures 1-5, 7-17 by E. Emmons; 6 by B. P. Whitfield.) 
Genus SPIRIFEE, Sowerby. 
Page 1. 
Spirifer arenosus, Coiii-iid. 
1. An individual with most of the brachial valve removed ; showing the brachial cones encrusted 
with silica. 
2. An internal silicious cast from which the calcareous spiral ribbon has been naturally removed, ex¬ 
hibiting the casts of the conical cavities. 
3. A silicified specimen ; showing a portion of the spiral cones. 
4. A larger example, slightly reconstructed from a silicified interior; showing the long crura, the 
disconnected jugal processes, the form of the ju-imary lamelliE and the shape and direction of 
the cones. 
Oriskany sandstone. Cumberland, Maryland. 
Spirifer audaculus, Com-acl. 
See Plate 24. 
5. A preparation, showing the'character of the brachidium. (c.) 
Hamilton group. Canandaigua Lake, N. Y. 
Spirifer IIuNGERFOiim, Hull. 
6. A specimen with the brachial valve removed ; showing the form of the brachidium. 
Upper Devonian. Rockford, Iowa. 
Spirifer gregarius, Chipj). 
7. A preparation, showing one of the spiral cones, with its jugal process and crus. X 2. (c.) 
Corniferous limestone. Falls of the Ohio. 
Spirifer mucronatus, Conrad. 
8. A preparation, showing the foi-m and size of the primary lamellse and the long, tapering spiral 
cones, (c.) 
Hamilton group. Canandaigua Lake, N. Y. 
Spirifer granulosus, Conrad. 
See Plate 23. 
9. 10. Two views of a preparation, showing the form and direction of one of the spirals, (c.) 
Hamilton group. Petosky, Michigan. 
11, 12. A preparation, showing the length of the crura, jugal processes and the narrow, small primary 
lamellae, (c.) 
Hamilton group. Canandaigua Lake, N. Y. 
Spirifer ligus, Owen. 
See Plate 22. 
13. A preparation, showing the crural bases, their attachment to the crura, and the form of the spiral 
cones which appear to have been somewhat disturbed toward the apices, (c;) 
Hamilton group. Independence, Iowa. 
Spirifer subumbona, Hall. 
14. A preparation, showing the lax coil of the spiral. X 4. (c.) 
Hamilton group. Western Hew York. 
