POLYGYRA. 151 



toward the aperture, and on its last third constantly marked on the 

 convex side, by a strong depression ; lip visibly thickened but not 

 reflexed. Alt. 5, diam. 16 mill. It was collected in the humid 

 forests covering the foot of the eastern chain of the Bolivian Andes, 

 north of Cochabamba. 



The figures in Fer. Hist., t. 69, f. 3 are copied from Orbigny's 

 plate ; Reeve figures and describes the true helicycloides. 



Genus POLYGYRA (Vol. Ill, p. 128.) 



P. AURICULATA var. MICROFORIS Dall (p. 138), not microformis. 

 P. DISSECTA Martens. PI. 42, figs. 21-24. 



Shell narrowly and deeply umbilicated, subdepressed, lightly 

 striatulate, tawny-corneous, somewhat shining ; spire shortly conoid ; 

 whorls 5J, slightly convex, the last rounded with very convex base ; 

 deflexed and constricted behind the aperture. Aperture very 

 oblique, wide-lunate; peristome reflexed, white; parietal wall 

 provided with a rather simple oblique fold ; outer margin having 

 two low subelongate denticles, parallel to the margin and separated 

 by a narrow triangular slit; basal margin having one obtuse small 

 denticle. (3/fe.) Alt. 3, greater diam. 9, lesser 7 2 mill. 



Toluca, central Mexico. 



Polygyra dissecta MTS., Biol. Centr. Amer., Mollusca, p. 167, t. 7, 

 f. 7, 7 arc. 



Described from one specimen. In general appearance very like 

 H. plagioglossa, but to be distinguished by the two laminar teeth on 

 the outer margin. 



P. RICHARDSONI Martens. PI. 42, figs. 17-20. 



Shell obstructedly umbilicated, subdepressed, lightly striatulate, 

 tawny-brown, slightly shining ; spire shortly conoid ; whorls 5, 

 slightly convex, the last rounded, very convex beneath, at the aper- 

 ture distinctly striated, deflexed and constricted. Aperture very 

 oblique, lunate ; peristome reflexed, white ; parietal wall provided 

 with an unequally two-limbed fold, outer lip with a moderate obtuse 

 tooth, prolonged upward into a lamina parallel with the margin ; 

 basal margin having one vertical, subcompressed, moderate tooth. 

 (Mts.} Alt. 4-5, greater diam. 9-11, lesser 8-9 mill. 



Presidio de Mazatlan, State ofSinaloa, Mexico. 



Polygyra richardsoni MTS., Biol. Centr. Amer. Molt., p. 168, t. 7, 

 f. 9, 9a-c. (April, 1892.) 



