302 



Chemnitz's name being non-binomial cannot stand. Sowerby 

 (1822) lists Limnea (Physa) rivalis as 'a species which has been 

 admitted into the English catalogue, but we only know it to be 

 found in Guadaloupe.' Subsequent authors have credited 

 rivalis to Sowerby on the basis of this work. The figures given 

 by Sowerby are excellent and as this constitutes the first recogniz- 

 able figure of the West Indian form (in lieu of any description), 

 the species really dates from Sowerby, but the name, of course, 

 must be tabled as a homonym. The younger Sowerby (1873, 

 species no. 31) also added to the confusion by quoting the earlier 

 Sowerby, as to the name P. rivalis, but giving an entirely new 

 locality, namely, Columbia River. This error was later copied 

 by Clessin (1886, p. 331) who regarded P. rivalis as a good species, 

 though elsewhere (1886, p. 281) he treats it as a synonym of 

 P. sowerby ana, referring in both cases to the same figure con- 

 tained in The Genera of Recent and Fossil Shells. The first 

 available name for this West Indian form seems to be Physa 

 marmorata Guilding. The synonymy would then be as follows: 



Physa marmorata Guilding. 



1822 Limnea (Physa) rivalis Sby., Genera of Recent and Fossil 

 Shells. London, Limnea. non Bulla rivalis Turton, 

 British Fauna, p. 169, 1807; non Bulla rivalis Mat. 

 and Rack., p. 126, 1807; non Physa rivalis Potiez 

 and Michaud, Galerie des Mollusques, vol. 1, p. 226, 

 pi. 22, fig. 21-22, 1838. 



1828 Physa marmorata Guilding, Zoological Journal, vol. 3, p. 

 534. 



1845 Physa brasiliensis 'Koch', Phil.-Conch. Cab. (2), vol. 1, 

 pt. 17, p. 10, pi. 1, fig. 18. 



The distribution of Physa marmorata Gld. seems to be quite 

 general as it is known from several of the Lesser Antilles and the 

 northeastern part of South America. The following records are 

 known (all being listed as P. rivalis Mat. and Rack.) : Trinidad, 

 (Guppy); Brighton, Grenada (E. A. Smith); Antigua (Pilsbry 

 and Brown) ; St. Thomas (E. A. Smith) ; Para, Papary Lake and 

 .Ceara-Mirim, all in Brazil (Fred Baker). 



This species is quite possibly a member of the genus Aplexa. 

 Shell characters alone, however, are not sufficiently diagnostic 



