1TO 

 PLEUROTOMARIA AGAVE. (N. sp.) 



Fig. 153. Fig. 154. 



Fig. 153. Pleurotomaria Agave. 



154. P Dryope. a and 6, different views of the same specimen. 



Description. Lenticular, with an acute margin ; apical angle, from 

 125 to 145 ; whorls three, forming a nearly smooth slope from the apex 

 to the margin. On the upper side the last whorl is gently concave in the 

 outer half, or two-thirds of the width, and slightly convex or flat above ; 

 in some specimens the concavity occupies the whole width ; upper whorls 

 gently convex or flat ; apex generally rounded. The margin in the last 

 whorl is thin, sharp, and a little turned upwards. On the underside the 

 whorls are convex, most prominent a little within the mid-width where 

 they are obtusely rounded angular. Umbilicus a little more than one- 

 third the whole width, exposing the rounded inner edges of all the whorls 

 to the apex. Aperture rhomboidal. Surface with fine striae curving 

 backwards to the margin. 



Width of an average specimen 22 lines ; height 10 lines ; width of 

 last whorl, on the upper side at the aperture, 7 lines. The width appears 

 to be from 15 to 24 lines ; the most common 20 lines. 



P. lapicida (Salter) is smaller and has the aperture more nearly 

 elliptical, and a much narrower umbilicus. 



P. Americana (Billings) has the outer margin rounded. 



P. aperta (Salter) has the whorls more slender, and the umbilicus 

 wider. 



Locality and Formation. Naquareau River, above Red River; Trenton 

 limestone. 



Collector. J. Richardson. 



PLEUROTOMARIA DRYOPE. (N. sp.) 



Fig. 154. o, b. 



Description. Shell turbinate ; spire depressed conical ; apical angle 

 about 100 ; whorls three. On the upper side the whorls are concave for 

 three-fourths their width ; the inner one-fourth next the suture convex. 



