PLATE 21—Continued. 
Figs. 10. (9, 11, 12.) Chonetes coronata.. 
10 a, b. Dorsal and ventral views of a small individual of this species. 
10 c, d. Yentral and profile views of a specimen of medium size and somewhat more than usual 
gibbosity. 
10 e, f. A ventral and profile view of a specimen which is more extended on the hinge line, and 
a little less gibbous than the preceding. 
10 g. A dorsal view, showing the area, etc., of a specimen which is unusually short on the 
hinge line. 
10 h, i. The exterior and interior of a large ventral valve. 
10 fc. Interior of a dorsal valve of medium size, showing a quadruple germination to the cardinal 
process. 
10 l. Interior of a larger dorsal valve where the cardinal process has only two divisions. The 
reniform muscular impression, characteristic of the genus,'is very distinctly shown. The 
foregoing specimens are all from the soft shales of the formation in New York. 
The following are introduced for comparison with authentic specimens of C■ coronata . 
9 a. b. Ventral and dorsal views of C. tuomeyi. These specimens and the two following 
figures are from Bake-oven, Ill., the original locality of the species, labelled by Messrs. 
Norwood & Pratten, and received from Dr. Norwood. 
11. A ventral valve of C. maclurea. 
12. Ventral valve of C. martini , partially denuded of its shell. 
Page 
133 
Fig. 18. 
Chonetes syrtalis (referred to) ... 138 and 135 
13 a, b. Exterior of shells of this species. 
13 c. Casts of a ventral valve of the same. 
13 d. A cast of the interior of a dorsal valve. The outline of the reniform impression is not 
distinctly preserved, and in consequence presents a different expression from fig. 10 l. 
