400 Systematic Paleontology 



Actii'on i/abbana Whitfield is smaller than A. linteus Conrad, more 

 slender, and more cylindrical, with a fainter and more irregular spiral 

 sculpture. 



Occurrence. — Monmouth Formation". Brightseat, Prince George's 

 County. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences. 



Outside Distribution. — Monmouth Formation. Xavesink marl, New 

 Jersey. 



Family R1NGICULIDAE 



Genus R1NGICULA Desliayes 

 I Hist, des Animaux sans Vertebres, 2d ed., 1838, vol. viii, p. 342] 



Type. — Auricula ringens Lamarck. 



Shell small, ventricose, spire relatively short; nucleus heterostrophous ; 

 surface of shell smooth or spirally striate; aperture narrow, parallel to 

 the axis of the shell, dilated and more or less emarginate anteriorly ; outer 

 lip thickened and reflected, smooth or finely plicate within; columella 

 excavated, calloused, furnished posteriorly as a rule with a strong tuber- 

 cular denticle and anteriorly with two prominent, transverse plaits. 



The genus has been noted in the Cretaceous deposits of Europe and 

 India as well as in those of North America. Some seventy species are 

 reported from the various Tertiary horizons, and about thirty-five from 

 the temperate and tropical waters of to-day. 



PiINGICULA CLARKI n. sp. 



Plate XVIII, Figs. 1, 2 



Description. — Shell rather large for the genus, ovate in outline ; spire 

 moderately high, its altitude a little less than half that of the entire shell ; 

 whorls five or six in number, subtrapezoidal, obscurely shouldered; 

 external surface highly polished, sculptured merely with two or three 

 feebly impressed spirals in front of the sutures of the later whorls and 



Etymology: Ringor, to show the teeth. A probable allusion to the promi- 

 nent tooth borne upon the posterior portion of the labium. 



