PLATE XI. 



Plattostoma UNI8ULCATA var. 



r«ge 27. 

 Fljr. 1- A|>ertnral viev, showing- the g«nci-al foi-m aiul elevation of the shell, the columella, etc. 

 Fijf. "J. Ttif Iiiii-k of the same specimen, showiuff the angulaiity of the volution. 

 Fig. 3. The njiire. 



Plattostoma LiNEATA.var. sinuosa. 



Page 44. 

 Fi(f. 4. Front view of a small sjieoiinen with a depi-eK.sed spire. 



Fijf. 5. Basal view, showing- the deep sinus in tlie aj)ertvii-e. Hamilton gnrap, Livingston county, N. Y. 

 Figs. 6, 7. Aiiortnral view and 8))ii'e of a larger specimen, with much higher spire and rounded volutions. 



From the Hamilton grou]), Canandaig-ua Lake, N. Y. 

 ¥\g. 8. Basal view of the same, showings the deep sinus of the lip. 



Plattostoma aplata. 



Page 20. 

 Fig-. 9. The spire of an imperfect spedmen. From the Schoharie g^t, Schohai-ie, N. T. ' 



Pleurotomaria ? sp.? 



yaticopgiif cretacea. Hall. Illustrations of Devonian Fossils: Gasteropoda, pi. 11. 1876. 



Not NaticopsU eretacea, H. & W. Twenty-thii-d Rep. N. Y. State Mus. Nat Hist., p. 240. 1873. 



Not Xaticopsis llBvis, Mbbk. H. & W. lb. Explanation pi. 12, figs. 3-5. 

 Fig. 10. The spire of an imjierfect cast referred with doubt to this species. 

 Fig. 11. Front view of the same, showing the obliquity of the shell and the substance of the callus filling the 



umbilicus. Upi>er Helilerberg limestone near Clarence Hollow, N. Y. 

 Figs. 12, 13. Two views of an internal cast. Upjier Helderberg limestone neai- Columbus, Ohio. 



Strophosttlus unicus. 



Page 30. 

 Fig. 14. Front view of the typical specimen, showing the columella and the form of the shell. 

 Pig. 15. Summit view of the same specimen. From the Schoharie grit, Schohaiie, N. Y. 



STROPHOSTTLtrS VABIAN8. 



Page 31. 



Figs. 16, 17. Two views of a young, vet^' oblique specimen, showing, in fig. 16, the peiistome nearly detached 



from the body of the pi-eceding- volution — an exceptional feature. 

 Fig. 18. Knlargement of the sui-face strite from a small, well-preserved specimen. 

 Yig%. 19, 20. Two views of a larger specimen, showing the jieiistome more completely united to the preceding 



volution. 

 Fig. 21. A medium-sized specimen, showing very great obliquity of the last volution and a slight separa- 

 tion of the iwsnstome from the body-whorl. 

 Figs. 22-24. Other examples, showing the form of the shell and the very broad umbilicus. 

 Pig. 20. A small Pi>ecimen, showing sti-ong plications near the ajierture, indicating the existence of a notch 



in the peristome during the later jieriod of its growth. 

 Fig. 26. A large anil more rotund sj«'cimen, showing an injury to the peristome during growth. 

 Figs. 27, 28. Two views of a large, w-ell-f'ormed, mtund specimen. The second tigui-e shows the obliquity 



of the outer lip to the axis of the shell. 

 Pigs. 29, 30. Two views of a large 8])ecimen, the latter showing the inner lip spreading over the preceding 



volution. 

 Fig. 31. A large oblique opnclmfin with the ppristonlfl milch thick«»rt(»d. 



The Riwcimens ai-e all from the Uiipor Meldei'becgf limestone, Onondaga county, N. Y. 



