626 



NORTH AMERICAN INDEX FOSSILS. 



FlG. 844. Phrag7nostoma chautauquce, (After Clarke. ) 



XXIV. Carinaropsis Hall. 

 Patelliform shells with apex slightly enrolled in median plane, 

 aperture flaring, emarginate anteriorly ; dorsal surface angular 

 medially ; a strong concave septum constricting the aperture below 

 the beak ; septum carinated on inner side. Operculum generally 

 present. Ordovicic. 



75. C. carinata Hall. Ordovicic. 

 Gradually expanding from minutely enrolled apex ; faint anterior 



sinus and strong dorsal carina. 

 Trenton of New York. 



76. C. cunulae Hall. (Fig. 845, a-c.) Ordovicic. 



FlG. 845. a-c, Carinaropsis cunulce, c showing sharp dorsal band ; d-g, C. cymbula. 

 f> g, a broken specimen showing septum ; b and <?, sections (<?= outline of operculum, 

 arb. ). (After Ulrich, Pal. Minn. ) 



Dorsum faintly subcarinate, the carina often replaced by a slit- 

 band ; septum broad, but slighty excavated. 



Trenton of Tennessee and Kentucky. 

 77. C. cymbula Hall. (Fig. 845, d-g.) Ordovicic. 



Like the preceding, but septum deeply excavated on the outer, 

 and strongly carinated on the inner side. 



Trenton of Kentucky, etc. 



