62 NORTH AMERICAN INDEX FOSSILS. 



21. P. guelphensis Whiteaves. (Fig. 91.) Siluric. 

 Long slender corals from 3 to 7 mm. in diameter. Epitheca 



with transverse constrictions and reelevations at irregular intervals, 

 but no longitudinal ribs. 



Common in the Guelph beds of Canada, Wisconsin, Ohio, etc. 



VIII. Chonophyllum E. & H. 



Generally top-shaped or subcylindrical corals composed of 

 invaginated funnels. Calyx large with numerous uniform septa. 

 Margins of old funnels not projecting. Sil.-Dev. 



22. C. niagarense (Hall.). (Fig. 92.) Siluric. 

 Cylindrical in the upper portion with frequent constrictions, 



septa subdued, spiniform, with notched margins, extending to the 

 center of the deep calyx. 



In the Niagara formation of Western New York, Kentucky, etc. 



23. C. magnificum (Billings). Middle Devonic. 

 Large, top-shaped, with a spreading basin-shaped calyx. Septa 



thickening outward. 



In the Onondaga beds of Michigan, Indiana and the Falls ot 

 the Ohio. 



IX. Ptychophyllum E. & H. 



Similar to Chonophyllum but with the septa twisted into a 

 pseudo-columella, at the center. Sil.-Dev. 



24. P. stokesi E. & H. Middle Siluric. 

 Conical with a deep spreading calyx, furnished with low, broad 



septa and a large pseudo-columella. Epitheca with root-like 

 processes. 



In the Niagara beds of Drummond Island, Mich., and Louis- 

 ville, Ky. 



X. Cystiphyllum Lonsdale. 



Simple or compound corals, varying from depressed turbinate to 

 cylindrical or irregular growth. Entire interior of coral filled with 

 vesiculose tissue with a cone arrangement of the vesicles. Calyx 

 without septa or with only faint ridges as in Chonophyllum, from 

 which genus it is probably derived. A strongly wrinkled epitheca 

 is present. Sil.-Dev. 



