PLATE 22. 
Page 
129 and 142 
Figs. 1-5. Chonetes setigera, 
1. A ventral valve enlarged to two diameters, showing two spines on each side of the apex. 
2. A more transverse form of the same (natural size), the spines not being preserved. These 
specimens are from the Chemung group near Meadville, Pa. 
3. A specimen preserving three spines on each side of' the beak. This specimen is from Pen- 
field, Ohio, and has the general features of C. setigera, but there may be some question 
as to absolute identity. 
4. A small individual (twice enlarged) from Painted Post, N. Y. This, and other specimens 
from the same locality, are proportionally longer than the typical forms. 
5. A portion of the surface striae of a specimen from the Marcellus shale, six times enlarged. 
Figs. 6-11. Chonetes scitula. 130 and 141 
6. A cast of the ventral valve of a very transverse specimen, twice enlarged; the spines are very 
short. 
7. A specimen having the base a little more rounded than is usual in this species; twice en¬ 
larged. 
8. A specimen of the natural size; which is slightly distorted. From shales of the Chemung 
group near Tioga, Pa. 
9. An enlargement to two diameters from a cast, of this species, showing the muscular and vas¬ 
cular impressions. The specimen is. from the Hamilton group in Virginia, and has a 
more rounded outline than the prevailing forms in New York. 
10. A cast of this species, preserving strong marks of the surface: striae, and casts of the spine 
tubes in the area. Chemung group, Cattaraugus county, N. Y. Enlarged. 
11. An enlargement of the area and upper portions of a specimen from the Hamilton group; show¬ 
ing the area, foramen and cardinal process; the spine tubes of the area in their inclinat ion 
towards the apex of the valve, and the bases of some of the spines turning directly out¬ 
wards from the margin. (See pages 116 and 117.) 
Figs. 12, 13. Chonetes lepida. 132 and 142 
12. A specimen from the Marcellus shale, twice enlarged. 
13. A specimen from the Chemung group at Forestville, six times enlarged. The specimens of 
this species in the Chemung group are minute, with the striae coarser than those of 
Hamilton group, but otherwise having similar features. 
Figs. 14, 15. Chonetes illinoisensis (referred to) . 145 
14. An individual from which the spines have been removed; natural size. 
15. A specimen of somewhat different form, preserving the spines of the hinge line; twice en¬ 
larged. These specimens are from the shaly sandstones of Eastern Ohio, associated with 
C. logani. 
Figs. 16-28. Chonetes logani var. aurora. 137 
16. A specimen of natural size. 
17. A specimen enlarged to three diameters. 
18. An enlargement to six diameters of the surface striae. The preceding figures are from 
specimens in the Tully limestone of New York. 
