Maryland Geological Survey 431 



the genus, however, and the sides of the body are flattened instead of 

 broadly inflated. 



Occurrence. — Monmouth Formation. Brooks estate near Seat Pleas- 

 ant, Prince George's County. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Xatural Sciences. 



Outside Distribtition. — Ripley Formation. Exogyra costata zone, 

 Union County, Mississippi. 



Liopeplum cretaceum (Conrad) 



Plate XV, Fig. 5 



Volutilithes cretacea Conrad, 1858, Jour. Acad. Nat. Sci., Phila., vol. iii, p. 

 333, pi. xxxv, fig. 16. 



Description. — " Fusiform ; spire elevated ; volutions contracted beneath 

 the suture, irregular longitudinal ribs on the upper volutions. Length of 

 fragment, 2| in." — Conrad, 1858. 



Type Locality. — Owl Creek, Tippah County, Mississippi. 



Shell thin, highly polished, broadly fusiform dorso-ventrally com- 

 pressed ; aperture little more than half as high as the entire shell ; whorls 

 closely appressed, probably about six in number, subtrapezoidal in outline, 

 those of the spire increasing uniformly in size, the body whorl very 

 feebly constricted upon merging into the pillar ; external surface smooth, 

 excepting the broad and somewhat irregular, incremental corrugations; 

 growth sculpture very prominent upon the later portion of the ultima, the 

 incrementals broadly arcuate and parallel to the margin of the expanded 

 outer lip; feeble fortuitous spirals occasionally developed at the base of 

 the pillar; suture lines very closely appressed, the zone of appression 

 approximately one-third the altitude of the entire whorl ; aperture broadly 

 lenticular ; outer lip arcuate, abruptly constricted anteriorly ; inner lip 

 smoothly concave at the base of the body ; pillar straight, biplicate ; ante- 

 rior extremity squarely truncate. 



