4 PROCEEDmGS OF THE NATIONAL MUSEUM vol.82 



in the Upper Amazon region of Peru, and that species also probably 

 belongs in Shepj^ardiconcha. The species attains a much larger size 

 than that of the type. A fragment consisting of little more than 

 a single whorl has a diameter of 13 mm. 



POTAMOLITHOIDES, new genus 



Shell small, resembling Potamolitlius but with spire depressed 

 and base widely umbilicate or deeply excavate. 



Type species. — PotamoUthoides hiblianus, new species, described in 

 this paper. 



POTAMOLITHOIDES BIBLIANUS, new species 

 Plate 1, Figures 1-3 



Shell small, somewhat beehive form. Apical whorls depressed, 

 planorbiform, the embryonic whorl slightly sunken. Whorls rap- 

 idly increasing, flattish on the upper surface, body whorl large, 

 subangular at the periphery, sutures linear. Base flat, widely umbil- 

 icate (or deeply excavate). Aperture oblique, outer lip thin, basal 

 lip sinuate. Parietal wall with a thick, upstanding callus which 

 makes the peritreme continuous. 



T'lfpe.—V.S.'NM. No. 372840 measures: Height, 3.5 mm; greater 

 diameter, 5 mm. It and many paratypes (U.S.N.M. No. 372841) 

 come from Biblian, Province of Canar, Ecuador. The largest para- 

 type measures : Height, 5 mm ; greater diameter, 7 mm. 



Remarks. — This is a fresh-Avater mollusk. Among recent shells 

 its nearest relative seems to be Potmnolithus.^ of which many species 

 occur in the La Plata drainage, Uruguay, and southeastern Brazil. 

 It may belong in the family Amnicolidae. 



Genus POMACEA Perry 



POMACEA BIBLIANA, new species 



Plate 1, Figitres 4, 5 



A mold showing that the shell had a depressed, nearly flat spire, 

 rapidly increasing whorls, and ample body whorl which formed 

 two-thirds of the whole shell, and a wide umbilicus. (The sub- 

 angular periphery in front of the aperture is probably due to the 

 whorl having been subject to pressure.) 



Type.— U.S.N.M. No. 372842 measures: Height, 20 mm; greatest 

 diameter, 30 mm. It comes from Biblian, Province of Canar, 

 Ecuador. 



Re-marks. — There is no doubt that this is a Pomacea (until re- 

 cently better known as Ampullaria) and therefore of fresh- water 

 origin. While only a mold it is deemed w^orthy of description, as 

 it affords additional evidence that the formation was derived ex- 

 clusively from fresh-water deposits. 



