4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.69 



ing granulose striae. With sufficient magnification the granules are 

 seen to be > shaped, with the point directed toward the right-hand 

 side of the whorL Most of them are of a ricli chestnut color and in 

 spots where large numbers of them are preserved they give a velvety 

 appearance to the surface. Aperture large, about seven-tenths the 

 length of the shell, its outer lip flaring, its columellar lip thick and 

 rounded and so formed at its upper end as to have the appearance 

 of covering an umbilicus; parietal w^all with a thick, white callus. 

 General color ashy and brownish, with many revolving, chestnut- 

 colored bands, which show prominently on the inner portion of the 

 outer lip and less distinctly for some distance within the shell. 



The type. Cat. No. 362863, U.S.N.M., measures: Length, 53 mm.; 

 diameter, 43 mm. ; length of aperture, 36 mm. 



It comes from Cienaga Totuma, Department of Atlantico, United 

 States of Columbia and was collected and presented by T. A. Link. 

 Its nearest relative is Aiyhpullmria pealeana Lea, than which it is 

 much larger, more globose, thicker, of darker colors and has more 

 numerous bands. 



In addition to the fine axial sculpture of growth striae mentioned 

 in the description there is a still finer axial sculpture, which shows 

 in spots, especially above the suture, and which requires a com- 

 pound microscope to reveal it. This sculpture consists of flattened 

 threads, of which there are some 75 to the millimeter and seems to 

 be in the calcareous portion of the shell and not in the periostracum. 

 The threads are about three times as wide as the intervening spaces 

 and are so uniform in width that apparently thej^ were formed with 

 mathematical precision. This sort of structure has been found in a 

 number of species of Ampullaria and probably each thread repre- 

 sents the unit of advance in growth of the shell. 



NEPHRONAIAS LEMPENSIS, new species 



Plate 2, figs. 4, 6 ; plate 3, fig. 4 



Shell rather compressed, nearly elliptical in outline, rounded at 

 both ends, the posterior end very slightly narrower than the anterior. 

 Dorsal and ventral margins about equally curved, both of them 

 rounding into the anterior and posterior margins as in an ellipse 

 and with no tendency to an angle of any kind. Shell rather thin 

 at the posterior end, moderately thickened at the antero-ventral por- 

 tion. No distinct anterior and posterior ridges, the disk of the valve 

 blending gradually into the anterior and posterior dorsal areas, the 

 descent at front being rapid, at the rear gradual. Beaks low, eroded, 

 located at the anterior third of the shell. Periostracum somewhat 

 clothlike, not glossy, but with a slight sheen. Color nearly uniform 

 chestnut, with faint indications of rays of green. (In younger 



