352 Fossils of the Calciferous Sandooch 



i 



Base s'ightly concave. Height of only specimens collected four* 

 teen lines, width of base about the same, width of umbilicus one 

 line. 



The spire of this species, owing to the perfect flatness of the 

 whorls, presents at first sight an uniform plane surface, the suture 

 being so fine that it is barely visible. The outer edge of 

 the body whorl shows what may be called a spiral band, which 

 on its upper side is bordered by a fine continuous line, half 

 a line from the edge ; the outer angle of the mouth has a moderately 

 deep angular notch as in the other species of this genus ; the 

 striae on the base after leaving the edge curve abruptly forward, 

 and then at the distance of less than a line from the edge rather 

 suddenly change their direction, and with a barely preceptible 

 backward curve proceed to the umbilicus in a nearly straight line ; 

 there are several strong wrinkles that follow in the direction of 

 the striae. The course of the striae over the edge cannot be dis* 

 tinctly seen but they appear to make a sharp curve backward cor- 

 responding to the form of the notch. The upper and outer 

 sides of the aperture are straight, the lower side is also straight 

 for about half the width of the volution, and it then curves up 

 gradually to form the inner lip, a small portion of which is reflect- 

 ed. This species much resembles a Trochus, but the notch in the 

 outer angle of the aperture, the direction of the striae on its sur- 

 face and the apparent band shew that it is more likely a Pleuroto* 

 maria. 



Dedicated to the eminent geologist Professor A. C. Ramsay, 

 Director of the Geological Survey of Great Britain. 



Locality and formation. — Mingan Islands, Calciferous Sand- 

 rock. 



Collectors. — Sir W. E. Logan, J. Richardson. 



Pleurotomaria, calcifera, (N. s.) 



Fig. 5. 

 a Pleurotomaria calcifera. 

 h A more depressed variety, 

 c View of the spire shewing the backward curving striae. 



