192 SYSTEMATIC PALEOXTOLOGY 



volving lines with narrower intersjDaces and 25 curved longitudinal 

 ribs on the body whorl; varices 270° apart, earlier ones obsolete; mouth 

 subquadrate; anterior canal broad and short; labium with a thick callos- 

 ity; columella very concave, with a sharp plait at the base, a large tooth 

 immediately above the plait and a small tooth in the center of the con- 

 cavity; labrum thick, lirate; spire short but sharp with concave sides; 

 whorls of the spire with more angular shoulder and stronger longi- 

 tudinal ribs than the body whorl. 



Length, S mm. ; diameter, G mm. 



Occurrence. — Calveut Fokmation. Plum Point. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Nassa gubernatoria n. sp. 

 Plate XLIX, Fig. 2. 



Description. — Shell small, slender, thick, seven- whorled, body whorl 

 with about 15 broad, uniform, raised, revolving lines with interspaces 

 half as wide, and very faint irregular longitudinal undulations; mouth 

 small; anterior canal broad and very short; labium strongly callous, 

 with a large tooth at the top; lal)rum very thick, with about five strong 

 lirations extending far in. 



Length, 9 mm. ; diameter, 4 mm. 



Occurrence. — Choptank Fokmation. Governor Run (lower bed). 



Collection. — ]\Iaryland Geological Survey. 



Nassa trivittatoides (Whitfield). 

 Plate XLIX, Figs. 3, 4. 



Tritia trivittatoidea • Whitfield, 1S94, Mon. xxiv, U. S. Geol. Survej', p. 104, pi. xix, 



figs. 1-3. 

 Tritia trivittatoides, var. elongata Whitfield, 1894, Mod. xxiv, U. S. Geol. Survey, 



p. 10.5, pi. xix, figs. 4-6. 



Descnption. — " Shell small, elongate-ovate or pupseforu), not exceed- 

 ing half an inch in total length, and few examples reaching that size. 

 Wliorls about seven in number, including the mammillar apical one, 

 convex and moderately increasino- in diameter with increased number; 

 sutures distinct but not clianneled or grooved. Aperture less than one- 

 third of the entire length, tlie outer lip thickened and varix-like exter- 



