552 PATAGONIAN EXPEDITIONS I ZOOLOGY. 



a shell resembling Paludestrina or Bythinella, but differing by the penis, 

 which is not bifid, and has several lateral papillae or warts. 



We owe to Souleyet an excellent account of the anatomy of L. guadi- 

 cJiaudii, and Dr. von Ihering has published valuable notes on that of 

 several species of southern Brazil. Many other species are referred to 

 Littoridina from the resemblance of the shells and their distribution alone. 

 Most of them have been described under genera based upon European 

 types, such as Paludestrina and Hydrobia, which, so far as we know, differ 

 anatomically from the type of Littondina. Provisionally, therefore, we 

 refer to Littoridina all of the smooth, slender and thin oviparous Amni- 

 colinae of South America, having the lip simple. 



Most of the species are fresh-water forms, but a few live as well in the 

 brackish water of estuaries, or even in the salt water of sheltered bays. 

 They are known to extend from below the mouth of Santa Cruz River in 

 Patagonia north to Ecuador in the west, and to the state of Rio Janeiro, 

 Brazil, in the east. 



Many species of Littoridina have been described from the La Plata sys- 

 tem and the Sierras of western Argentina (Provinces of Cordoba and Men- 

 doza) by d'Orbigny, 1 Strobel 2 and Doering, 3 but none have heretofore been 

 reported from the southern territories. Mr. Hatcher's collections extend 

 the range of the genus south to the Mount of Observation, below the 

 mouth of the Santa Cruz River. 



Several species of Littoridina have both slender and stouter forms, 

 with others of intermediate shape, in any large lot. These differences 

 may be sexual, but no observations bearing on the point have been made. 

 In some other species the contour is nearly uniform. 



Various authors having referred the Littoridinae to d'Orbigny's Palu- 

 destrina, it may be well to give some account of that genus. 



Paludestrina was proposed by A. d'Orbigny in 1839* for Paludina 

 acuta of France and the South American rissoids of fresh and brackish 

 water, having the operculum spiral, such as P. lapidum, P. peristomata and 

 P. australis. Various subsequent authors have mentioned or discussed 



'Alcide d'Orbigny, Voyage dans I'Amerique Meridionale, Mollusques, 1839. 



2 Pellegrino Strobel, Materiali per una Malacostatica di terra e di acqua dolce dell'Argentinia 

 Meridionale. Pisa, 1874. 



3 Adolfo Doering, Apuntes sobre la fauna de moluscos de la Republica Argentina, in Boletin 

 de la Academia Nacional de Ciencias en Cordoba, VII, 1884, pp. 465-474 ("Hydrobia"). 



4 Voyage dans 1'Amerique Meridionale, Mollusques, p. 381. 



