PILSBRY: NON-MARINE MOLLUSCA OF PATAGONIA. 587 



penis of specimens from the Santa Maria River, near its confluence 

 with the Rio dos Sinos). 



? Lithoglyplms lapidum d'Orb., Clessin, Malak. Blatter, n. F., X, p. 170 

 (Guahyba debris ; Santa Maria River). 



"Shell inflated-conic, short, thick, smooth, spire conic, acute at the 

 summit ; whorls 5, convex, the last whorl usually depressed, all being parted 

 by a deep suture. Aperture round, ample, with thick borders, not reflexed. 

 The columella is calloused. Color uniform green. Operculum corneous, 

 flexible, spiral. 



"Alt. 5, diam. 4 mm. 



"This species is closely related to the preceding (P. peristomatus] by 

 its short shape ; it differs constantly by wanting a carina, and by the non- 

 reflexed peristome " (d'Orbigny). 



"P. lapidum inhabits the whole course of the Parana and La Plata, from 

 well above Corrientes to Buenos Aires, or from 27 to 34 S. lat; on 

 stones, clinging in great numbers to the under side, at extreme low water. 

 It moves quite actively" (d'Orbigny). 



The typical form of P. lapidum, figured by d'Orbigny, has an evenly 

 rounded last whorl, though his phrase, " le dernier [tour] est souvent 

 comme deprime," indicates that the Parana shells are frequently com- 

 pressed around the upper part of the last whorl. Mr. E. R. Sykes, who 

 kindly examined the types of the species for me, states that one specimen 

 is so characterized. The aperture is ample, the lip not in the least con- 

 tracted and not thickened, the columella only moderately thickened. 



The variety dunkeri of Strobel, from the Rio de La Plata at Olivos, near 

 Buenos Aires, seems to differ from P. lapidum only by its small size ; 

 length 4, diam. 3.5 mm., with 4 whorls. It was described from a single 

 individual,' and probably has no racial significance. 



I have not seen typical P. lapidum from the Uruguay River. 



In the State of Sao Paulo P. lapidum has been reported by several 

 authors from streams flowing into the Atlantic, as quoted in the references 

 above, which I am unable to control ; but I doubt whether the true P. 

 lapidum is found in those waters. 



A form of P. lapidum having the spire rather longer than d'Orbigny's 

 type figures is drawn in figs. 4, 5, 50 of Plate XXXIX. It is from the 

 Uruguay River, exact locality not noted. 



At Paysandu, Uruguay a race occurs differing somewhat from typical 



