POLYGYRA. 153 



TRIODOPSIS (Vol. Ill, p. 143.) 



This section includes the American species which Tryon has 

 >laced under " Isognomonostorna." The Old World forms, H. per- 

 and subpersonata belong to the restricted genus Helix, near 

 mpylwa, etc. The H. yucatanea Morel, (p. 146) belongs to the 

 T. texasiana group of section Dcedalochila. 



[. APPRESSA Say (p. 148). PI. 50, figs. 6, 7 (young.) 

 This species attains a very large size in some parts of the South. 

 Specimens from Woodville, Alabama, measure: alt. 10, diam. 21 mill. 



[. OBSTRICTA var. CAROLINENSIS Lea. PL 50, figs. 8, 9, 10. 

 Shell distinctly angulated at the periphery, strongly costulate 

 >ve, smoother below ; the dull upper surface sometimes showing a 

 iw sparsely scattered microscopic granules, under a lens. Aper- 

 ire having three strong teeth. Differs from typical obstricta in the 

 far less compressed peripheral keel ; from palliata in the very differ- 

 ent sculpture, etc. 



South Carolina. ' 



H. SARGENTIANA Johnson & Pilsbry. PL 50, figs. 1-5. 



Shell depressed, imperforate, lens-shaped, carinated. Surface 

 strongly rib-striate, the striation disappearing toward the center of 

 the base ; under a lens the surface between the rib-like striae is seen 

 to be finely granulated. The aperture is wide, oblique; lip broadly 

 reflexed, flattened, the basal lip bearing a long lamella, as in H. 

 appres*a. Upon the parietal wall there is a strong, high, curved 

 tooth, like that of If. elevata but longer. There are 6 whorls. The 

 color is light russet above, paler or whitish below. 



Alt. 11, diam. 24 mm. 



Alt. 12, diam. 24 mm. 



Alt. 9 diam. 22 mm. 



Woodville, Alabama. 



Helix sargenti J. & P., Nautilus vi, p. '8 (May, 1892). Not H. 

 sargenti BLD. H. sargentiana J. & P. t. c., p. 48. 



This species differs from H. appressa in its larger size, stronger 

 striation, and more especially in the granulated instead of spirally 

 striate microscopic sculpture, the strong carination, etc. It is allied 

 in shape and sculpture to H. carolinensis Lea, but differs in totally 

 lacking the upper lip tooth, in being flatter, more concave below, 

 etc. The young shells (pi. 50, figs 4, 5) differ markedly from 



