374 | MOLLUSCA. 
The living animal examined and figured by Strebel (loc. cit. p. 54) shows an indented 
margin of the mantle. 
P. strebeli comes very near P. cubensis, Pfr., from Cuba, which is, however, somewhat 
more shining, with a thinner and slightly arcuated columellar margin. 
18. Physa polakowskyi. (Tab. XX. figg. 14, 15.) 
Physa polakowskii, Clessin, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Limneiden, p. 352, 
t. 49. fig. 12 (1886); Biolley, Moluscos terr. y fluv. de Costa Rica, p. 18°. 
A small shell, pale yellow in colour, with rather convex whorls, deep suture, and a very thick, white, nearly 
straight columellar margin; a broad whitish callus on the inner wall of the aperture; a thin white deposit 
inside the outer margin. 
Long. 64-9, diam. 4-5; apert. long. 5-6, lat. 23-3 millim. 
Hab. Cuntrau Guatema.a: near the capital (H. Polakowsky, in Mus. Berol., 18771). 
CrentraL Costa Rica: San José, in the rivers Tiribi and Virilla, also in an irrigation- 
tube (Biolley 2). 
19. Physa tehuantepecensis. 
Physa tehuantepecensis, Crosse & Fisch. Journ. de Conch. xxix. p. 835 (1881) *; Miss. Scient. Mex., 
Mollusca, i. p. 106, t. 27. figg. 15a, b’. 
Somewhat biconical, the spire projecting as in typical P. osculans, and the lower half of the last whorl narrowed 
considerably downwards; outer margin of the aperture very little arcuated; columellar margin broad, 
nearly straight. 
Hab. 8.W. Mexico: Isthmus of Tehuantepec (Sumichrast ! 2). 
[20. Physa hjalmarsoni. 
Physa lyalmarsoni, Clessin, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Limneiden, p. 295, 
t. 42. fig. 6 (1885) %. 
Oblong-ovate, dull brown, with rather coarse whitish vertical striz; suture rather deep; columellar margin 
broad above, strongly twisted, white, below thin and arcuated towards the basal margin. 
Length of a specimen much worn at the apex 17, diam. 83; apert. long. 12, lat. 6 millim. 
Hab. * Honpuras (Hjalmarson *). 
Having examined the typical specimens, I cannot help thinking that this may be one 
of the numerous forms of P. proteus, Sow., and therefore of Australian, not American, 
origin. | 
Obs.—It may be here noted that Physa subarata, Menke [Synopsis Molluscorum, 
p- 132 (1830) ], from Cincinnati, according to a specimen given by the author in 1831 
to my father, and now in the Berlin Museum, belongs, without doubt, to P. ancillaria, 
Say, as figured by Haldeman (Monogr. Limn. t. 3. fig. 1), and not to P. heterostropha, | 
as was supposed by Haldeman and Binney. 
