652 



NORTH AMERICAN INDEX FOSSILS. 



XLVII. Ccelidium Clarke and Ruedemann. (Ccelocaulus , 



Oehlert.) 

 Differs from Hormotoma in greater length and more numerous 

 depressed whorls and perforated axis, small umbilicus and rounded, 

 not produced aperture. Ordovicic-Devonic. 



152. C. linearis (Bill.). Ordovicic. 

 More strongly embracing than the next, suture almost obliterated. 

 Beekmantown of Mingen Islands. 



153. C. oehlertiU. and S. (Fig. 893, a, b.) Ordovicic. 



Fig. 892. Ccelidium macrospira, longitudinal section, showing perforate axis, and 

 two more or less complete shells, showing form and surface character. (After Clarke 

 and Ruedemann, Mem. N. Y. State Museum, V.) 



Of numerous (30 ?) closely embracing compressed whorls, mak- 

 ing an apical angle of 12 . 



Galena of Illinois. 

 154. C. macrospira (Hall). (Fig. 892.) Siluric. 



Large, apical angle 20 to 25 °, early whorls embracing to within 

 one half shoulder width or less, later ones to two thirds shoulder 

 width or wider ; periphery subangular with faint band ; surfaces 

 above and below gently convex. 



Guelph of Canada, New York, Wisconsin, etc. 



