PLATE XLI 



PAGE 



Figs. 1-5. SPYBOCERAS CROTALUM (Hall) 314 



1. Fragment, showing the prominent annulations and longitudinal 



striae. 



2. Enlargement of same. X 2. 



Romney formation, Hamilton member, Western Maryland. 



3. Internal impression of portion of living chamber, showing absence 



of annulations near aperture and striate surface. 



4. A small, septate fragment, preserving the characteristic fine, longi- 



tudinal striae over the exterior of the tube. 



5. A small, slightly compressed specimen, showing the surface mark- 



ings and the increase in prominence of the annulations toward 

 the larger end. 



Hamilton formation, New York. 



Figs. 6-8. SPYROCERAS XUXTIUM Hall 316 



6. Partly exfoliated fragment, showing the surface striae. 



7. Shell of same enlarged, showing surface striae. X 6. 



Romney formation, Hamilton member, right bank of Potomac, 

 3 miles below Cumberland. 



8. A compressed specimen showing annulations and longitudinal striae. 



Hamilton formation, New York. 



Figs. 9-11. SPYROCERAS CLARKEI Prosser n. sp 317 



9. 10. Two views of fragment, showing five annulations and surface 



markings. 



11. Same enlarged, showing the longitudinal and concentric stria?. 

 X3. 

 Romney formation. Hamilton member, Ernstville. 



124 



