458 Systematic Paleontology 



approximately twenty-five in number upon the ultima, finest and most 

 crowded upon the appressed band, evanescent upon the summits of the 

 costte and somewhat wider and less regular upon the base of the body; 

 interspiral area linear or sublinear over the entire surface from the apex 

 to the anterior extremity ; aperture narrow, obliquely lenticular ; outer 

 lip symmetrically arcuate ; inner lip smoothly concave ; anterior canal 

 short, broad, ill-defined. 



Dimensions (slightly imperfect specimen). — Altitude 22.5 mm., maxi- 

 mum diameter 14.4 mm. 



Type Locality. — Brightseat, Prince George's County. 



This species is well characterized by the very prominent axial ridges 

 which strongly undulate the periphery of the ultima, and by the very fine, 

 spiral threading which covers the external surface. 



Occurrence. — Monmouth Formation. Brightseat, Friendly, McNeys 

 Corners, 1 mile west of Friendly, Prince George's County. 



Collection. — Maryland Geological Survey. 



Pykifusus vittatus n. sp. 

 Plate XV, Fig. 4 



Description. — Shell rather thick, crumbly, of moderate size for the 

 genus ; slightly compressed dorso-ventrally, ovate in outline ; aperture 

 about four-fifths as high as the entire shell; spire depressed, the whorls 

 rapidly enlarging, very closely appressed, submerged beyond the peri- 

 pherj', approximately five or six in number; body whorl broadly but not 

 very strongly inflated, slightly constricted basally; shoulder of the whorl 

 the only portion visible on the spire, forming a feebly convex area between 

 the sutures, the outline obscured, however, by the heavy sculpture; axials 

 approximately thirteen in number, nodulating the periphery of the whorl, 

 rapidly evanescing behind the periphery on the body, persisting as irregu- 

 lar, undulatory costss well down to the base of the whorl ; turns of the spire 

 so closely appressed that the posterior portion is more or less nodulated 

 by the cosfae of the preceding volution, leaving only the narrow medial 

 position of the shoulder free from axial sculpture; spirals not developed 



