30 FOSSILS FROM SOUTHERN UNITED STATES— BALL. vol.xvui. 



thick mass of callus, which is much thiuned auteriorly ; pillar thin, solid, 

 arched, with a narrow, long chink behind it; aperture rounded in front; 

 outer lip thin, sharp edged, simple. Longitude of shell, 4.5: maximum 

 diameter, 1.5 nmi. 



Eaintat. — Lower Eocene, Lisbon horizon, at the head of Saline Bayou, 

 St. Maurice. Winn Parish, Louisiana, collected by Johnson f station 

 2005). 



Type. — No. 100971, U. S. N. M. ; received from U. S. Geological Survey. 



This species is remarkable for the combination of characters ordina- 

 rily regarded as subgeneric or sectional. It has the form of BullineUa^ 

 but the j)osterior extension of the aperture is narrowed to a rounded 

 point, the spire is concealed, not marked by any pit or perforation, but 

 covered by a short, thick mass of callus ; finally, the shell is very nar- 

 rowly umbilicate, with a slender, arched, unplicate pillar, twisted, but 

 without the short, strong twist of typical Aiys. AVhen fully developed 

 the fringe like grooved area at the apical end is a strongly marked 

 character. 



ATYS OBSCURATA, new species. 



Shell small, wider than A. gracilis, and differing from it in having 

 the lateral profile evenly curved, so that no indication of the'equatorial 

 swelling is visible in it; the aj)erture is proportionately wider and less 

 produced behind, the inner lip above the spire is more strongly twisted; 

 there is a shallow pit, but no perforation, at the spire, nor is there any 

 thickened striated rim at the margin of the pit; the spiral grooving, 

 though similarly distributed, is rather sharper than in A. graciUs, and 

 the i)illar less obviously twisted; it is obliquely truncate, narrow, and 

 has behind it a narrow but obvious groove. Longitude, 4; maximum 

 diameter, U mm. 



Mabitat. — Lower bed at Alum IJluff (2211) and the Miocene marl of 

 Bowden, Jamaica (Bland). 



Types.— ^os. 015C3, 113893, U. S. K. M. 



Only two specimens were obtained at Alum Bluff, but the species 

 does not seem to stand in with any of the others. It is a typical Atys, 

 and not an Acrostemma. 



RETUSA (CYLICHNINA) DECAPITATA, new species. 



Shell small, subcylindrical, smooth, except for lines of growth, gen- 

 erally polished, with a few revolving stria* on the base; spire sunken, 

 perforate, below a very shallow pit with the edge more or less rounded 

 over; aperture as long as the shell, narrow; the outer lip shar^), 

 simple, straight, with a deep sutural sinus and anteriorly receding and 

 then rounding imperceptibly into the ])illar; pillar twisted, obscurely 

 ridged, with a minute chink behind it; the body with a thin wash of 

 callus. Longitude, 5.25; maximum diameter, 2 mm. 



Rabitat.—C\nl^o]^A beds (2213). 



Types.— ^os. 113886, U. S. N. M., and in Mr. Aldrich's collection. 



