MOLLUSCA. 667 



Pleurotomaria brittoni Whitfield. 



Plate LXXV., Figs. 10-12. 



1892. Pleurotomaria Brittoni Whitf., Pal. N. J., vol. 2 

 (Monog. U. S. G. S., vol. 18), p. 188, pi. 23, figs. 7-9. 



Description. — "Shell below a medium size, broadly conical in 

 form', rising from' a flattened base; the apical angle being about 

 80°. Volutions four, or from four tO' five in number, slightly 

 scaliform in character; the outer face being flattened or very 

 slightly convex, nearly in the direction of the spire, the upper 

 surface of any individual volution being a very little larger than 

 the basal edge of the next above it, and very slightly rounded on 

 the angle; suture lines distinct in the casts. Base flattened or 

 scarcely convex for two-thirds the width from the outer edge, 

 which is moderately sharp, and then rapidly rounding into* the 

 moderately sized umbilicus. Aperture obliquely quadrangular, 

 the inner basal or umbilical angle rounded. Slit of the outer lip 

 not definitely ascertained in any of the specimens, which are all 

 internal casts, but as nearly as can be ascertained has been -nar- 

 row and placed at the outer basal angle, and not extending back- 

 ward for more than one-third ol the outer volution. Surface 

 features unknown." (Whitfield.) 



Remarks. — Except in size, and in its proportionally more 

 highly conical form, the type specimen of this species resembles 

 Pleurotrema solariformis from the Vincentown sand, the aper- 

 tural slit, however, is continuous and is placed at the lower angle 

 of the volution, instead of being composed of a series of oval 

 perforations at the m'id-height of the volution. 



Formation and locality. — Manasquan marl, Farmingdale 

 (Whitfield). 



Geographic distribution. — New Jersey. 



Genus Pleurotrema Whitfield. 



Pleurotrema solariformis Whitfield. 

 Plate LXXV., Pigs. 13-14- 



1861. Architectonica Ahhotti Gabb, Proc. Acad. Nat. Sci. Phil. 

 (1861), p. 321. (In part.) 



