I 



PLATE 21— Continned. 



Pago 



Figi. 10. (9, 11, 12.) Chonetes coronata 133 



10 a, b. Dorsal and ventral views of a small individual of this species. 



10 c, d. Ventral 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 A, i. The exterior and interior of a large ventral valve. 

 10 k. Interior of a dorsal valve of medium size, showing a quadruple termination to the cardinal 



process. 

 10/. Interior of a larger dorsal valve where the cardinal process has only two divisions. Tlie 



reniform muscular impression, characteristic of the genus, is very distinctly shown. Tlie 



foregoing specimens arc 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. 6. Ventral and dorsal views of C- tuomeyi. These specimens and the two following 



figures are from Bake-oven, 111., the original locality of the species, labelled by Messrs. 



Norwood & Pratten, and received from Dr. Norwood. 



11. A ventral valve of C. maclurea. 



12. YeDtral valve of C. martiui, partially denuded of its shell. 



Fig. 13. ' Chonetes strtalis (referred to) 133 and 135 



13 a, b- Exterior of shells of this species. 

 13 c. Ca.«ts 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 dilTerent expression from fig. 10 I. 



