628 



NORTH AMERICAN INDEX FOSSILS. 



Large and high with nearly flat spire, sometimes with early 

 volutions elevated ; shoulder angle large, often 90 ; umbilicus 



Fig. 848. a, b, Raphistoma stamineum ; c, d, R. striatum. (After Raymond. ) 



closed except in internal molds ; surface with coarse rounded 

 striae or undulations. 



Chazy of New York and Quebec (Aylmer sandstone). 

 81. R. stamineum Hall. (Figs. 848, a, b\ 849.) Ordovicic. 



Fig. 849. Raphistoma stamineum. (After Hall.) 



Large, central portion of spire slightly elevated above outer 



volution ; body of whorl subventricose ; shoulder nearly flat ; 



angle sharp ; striae rounded. 



* [2 ^^^ Chazy of New York. 



M&M I 82. R. planistrium Hall. Ordovicic 



I f . M 1, Smaller than preceding, of greater proportional 



^| ™ ^F height ; shoulder slightly concave ; striae flat, 



Fig. 850. Raphis- imbricating ; aperture narrow, trigonal ; umbili- 



tomina attleborough- CUS small. 



^.enlarged. (After Qh q{ New Yo rk. 



Walcott, loth Ann. 



u. s. G. s.) S3. R. peracutum Ulrich and Scofield. 



(Fig. 851, a-d.) Ordovicic. 



Small, spire perfectly flat, shoulder angle very sharp ; umbilicus 

 above a fourth of diameter ; revolving line a third of the shoulder 

 width from the suture. 



Black River of Minnesota. 



