THE NAUTILUS. 79 



Limncea viator d'Orb. Montevideo : creek in the Prado. 



Planorbis heloicus d'Orb. Montevideo, back of Cerro. The 

 typical and a large less shining form, diam. 10 mm. 



Plmwrbis peregrin us d'Orb. Montevideo, back of Cerro. 



Planorbis paropseides d'Orb. (?). Creek in Prado, Montevideo. 

 Agrees well with d'Orbigny's description and figures, but on ac- 

 count of the locality may be a different species. 



Planorbis castaneoiiitens Pils. & Van., n. sj>. Near Maldonado. 



ANCYLID^E. 



Ancyhis obli/ji/i/s Brod. & Sowb. San Gabriel's Island, on stones 

 in Rio de la Plata. 



The specimens vary considerable in degree of curvature of the 

 apex, but are apparently all referable to this species, which was 

 originally described from Chili. 



AMPULLARIIDJE. 



Ampnllaria neritoides d'Orb. La Plata River, San Gabriel's 

 Island, Uruguay ; Uruguay River at Paysandu. Specimens with 

 the interior pure white as well as the usual purple form. 



Ampnllaria canaliculate Lam. Rio de la Plata at Buenos Ayres, 

 Palenno and Ensenada ; Parana near Rosario and at Paraiso. The 

 specimens vary from true canaliculata to the varieties insularum and 

 australis. 



Ampnllaria sp. A small form, not determined, occurred in the 

 creek in the Prado, Montevideo. 



Ampullaria Roissyi d'Orb. Parana River near Rosario, Santa 

 Fe province, Argentina. 



Ampullaria Spixii d'Orb. Parana River near Dos Hermanos 

 (" Two brothers ") Island. 



AMNICOLID^E. 



Littoridina australis d'Orb. Creek in the Prado, and in a small 

 spring back of the Cerro, Montevideo. We follow the usual identi- 

 fication in this case, although not at all sure of its correctness. The 

 larger specimens measure as much as 82 mm. alt. 



Littoridina ehamutnu d'Orb. (?). San Gabriel's Island. 



Littoridina Isabellei d'Orb. (?). San Gabriel's Island, with the 

 preceding. 



