PLANORBIS CORPULENTUS. 19 



vicinity of New Orleans: "South Carolina." — 

 Dr. R. E. Griffith. 



OBSERVATIONS. 



Distinguished from P. trivolvis, var. fallax, 

 by its greater size and density, the stronger de- 

 velopment of the upper carina, and of the lines 

 of accretion; the more open umbilic above, and 

 narrower and deeper excavation of the left side; 

 the shape of the aperture, the curvature of the 

 striae; and finally, by the greater constancy and 

 extent of the deflexion of the last turn, to the 

 left of the obverse plane of the shell. 



PLANORBIS CORPULENTUS, Say. 



Plate 3.— Figs. 7—9. 



P. testa magna, transverse latissima, supra late umbili- 

 cata, subtus excavata: anfractibus 4 — 5 biangulatis, sese 

 obtegentibus, rapide accrescentibus; rugis exaratis. 



SYNONYMS AND REFERENCES. 



F. CORPULENTUS, Say. Long's Expedition to the source 

 of St. Peter's river, p. 362, pi. 15, fig. 9. 



