PLATE 22. 



Pngo 



Figs. 1-5. Chonetes setioera 129 and 142 



1. A ventral valve enlarged to two diameters, showini; two spines on each side of the apex. 



2. A more transverse form of the same (natural size), the »))ines not being preserved. These 



specimens are Irora the Clicmung group near Meadvllle. Pa. 



3. A sjiecimen preserving three spines on each side of tlie beak. This specimen is from Pen- 



field, Ohio, and has the general features of C. tetigera, but there may be some question 

 as to absolute identity. 



4. A small individual (twice enlarged) from Painted Post, N. Y. This, and other s|>ecimcns 



from the same locality, are proportionally longer than the typical forms. 

 0. A portion of the surface stria: of a specimen from the Marcellus shale, six times enlarged. 



FiK8.6-ll. Chonetes 8CITULA ,, 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 ronnded than is usual in this species; twice en- 



larged. 



8. A specimen of the natural size, which is slightly distorted. From sliales 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 si>ecimeu is from the Hamilton group in Virginia, and has a 

 more rounded outline than the prevailing lornis in New York. 



10. A cast of this species, preserving strong marks of the surface stri«, and casts of the spine 



tubes in the area. Chemung group, Cattaraugus county, N. Y. Enlarged. 



1 1 . 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 inclination 

 towards the apex of the valve, and the bases of some of the spines turning directly out- 

 wards from the margin. (Sac pages 116 and 117-) 



Figs. 12, 13. Chonetes lepida 132 and 142 



12. A ispecimen 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 .strim coarser than those of 

 Hamilton group, but otherwise haviug similar features. 



Figs. 14, 15. Chonetes illinoise.nsis (referred to) 14.'» 



14. An individual from which the spines have been removed; natural size. 



16. A specimen of somewhat different form, preserving the spines of the hinge linit; twice en- 

 larged. These specimens are from the shaly sund.st^nes of Eastern Ohio, associated with 

 C. logani. 



Figs. 16-28. Chonetes looani var. aurora I:;? 



16. A specimen of natural size. 



17. A specimen enlarged to three diameters. ^ 



18. An enlargement to six diameters of the surface stria-. The preceding figures are from 



specimens in the Tully limestone of New York, 



