2 PROCEEDINGS OF THE NATIONAL MUSEUM Vol. 68 



LYMNAEA (PSEUDOSUCCINEA) APERTA, new species 



Plate 1. fig. 4 



Shell fragile, imperforate, much stouter and less elongate than 

 harheri; whorls rapidly descending, suture moderately, oblique, well 

 impressed, subcrenulate ; sculpture consisting of fine axial lines of 

 growth, and hints of spiral malleation. Aperture less than half 

 the length of the shell; about half as wide as long; its outer lip 

 thin, oblique to the axis of the shell, somewhat rounded, its basal 

 portion well rounded; columellar lip thin, less oblique than in 

 harheri; parietal wall with a thin glaze. 



The type, Cat. No. 353154 U.S.N.M. measures : Height, 17.5 mm. ; 

 diameter, 9 mm.; length of aperture, 11 mm. 



The name aj)6rta was suggested by the flaring aperture. This 

 shell shows a distinct relationship to columella Say and also to the 

 new species described above as harheri. It may be an ancestor of 

 colu7nella. 



PLANORBIS (PLANORBINA) PREGLABRATUS, new species 



Plate 1. figs. 1, 2. 3 



Shell large, much compressed vertically, sunken on both spire and 

 base. (In this description the shell will be treated as dextral, though 

 that is subject to doubt.) Whorls seven, a large portion of each 

 exposed in both the spire and the umbilicus; body whorl obtusely 

 angular above and below, its middle portion but slightly convex, 

 and the upper diameter much larger than the lower, making the 

 whorl generally oblique. In the tjq^e and some of the paratypes 

 the whorls in the spire and in the umbilicus overlap each other 

 irregularly, instead of each whorl being neatly affixed to the outer 

 surface of the preceding whorl. In other paratypes the growth is 

 regular. Sutures deeply impressed, giving the whorls a semisolute 

 appearance. Sculpture consisting of many fine, flexuous, retractive 

 growth lines, and nearly equally spaced riblets; at intervals the 

 striae across the bodv whorl arc more deeply impressed, indicat- 

 ing a short period of rest in growth. About halfway round the 

 bod}^ whorl a transverse thickening shows the point at which there 

 was a prolonged rest period. Aperture very oblique, lip simple, a 

 moderately thick callus on the parietal wall. Evidently, when living 

 the shell v\'as glossy, especially on its lower surface. 



The type, Cat. No. 353152 U.S.N.M. measures : Height, 10.5 mm. ; 

 diameter, 29.5 mm. Cat. No. 353153 includes 13 paratypes. 



The fact that this species is related to the recent shell P. glahratus 

 and preceded it in time is indicated by the name fveglahratus. It 

 is also closely related to P. conanil Dall of the Caloosahatchie beds 



