6 3 S 



NORTH AMERICAN INDEX FOSSILS. 



XXXIII. Phanerotrema Fischer. 

 Turbinate shells with few rapidly enlarging whorls, developing 

 a shoulder angle in the later whorls, slit band deep on the angle 



of the last whorls. Siluric-Carbonic. 

 in. P. occidens (Hall). (Fig. S66.) 



Siluric. 

 Angle extending back through most 

 of the whorls, final coil somewhat 

 loose ; shoulder flat but sloping, with 

 strong revolving spirals, cancellated 

 by growth lines ; body of whorls 

 rounded. 



Niagara limestone of Wisconsin. 



112. P. labrosa (Hall). (Fig. 867.) Devonic. 

 Large, last whorl very ventricose, angulation chiefly on last 



portion of outer whorl, spirals strong on all parts of shell, can- 

 cellating lamellae strong. 



Helderbergian (Becraft) of New York, etc. 



113. P. grayvillensis N. and P. Carbonic. 



Fig. 866. 

 dens, X 2 A- 

 Mus. Report 



Phanerotrema occi- 

 ( After Hall, 20th 



Fig. 867. Phanerotrema labrosa ; a, b, opposite views of a specimen partly denuded 

 of the shell, X i 5 c > enlargement of surface markings. (Pal. N. Y., III.) 



Small, high -spired; volutions all angular, shoulder slightly 

 concave ; spirals strong. 



Coal measures of West Virginia, Kentucky, Illinois, Indiana, 

 Iowa, Missouri, Nebraska, and Arizona. 



