396 MOLLUSCA. 
Hab. W. Guaremama: Lake of Duefias (Salvin ®). 
Crnrrat Nicaragua: San Agustin, near Acoyapa, in marshy pools (Zate"). 
Soutn AMERICA: Venezuela 2, N. Brazil, Paraguay. 
ANTILLES: Martinique (Candé). 
I have not seen Salvin’s or Tate’s specimens of this species, and I include it in our 
list solely on the authority of Fischer and Crosse, who, however, do not appear to have 
had Central-American specimens before them. For Strebel’s statement concerning it, 
quoted by Fischer and Crosse, consult the following. 
18. Planorbis sumichrasti. 
Planorbis, sp. ?, Strebel, Beitr. Mex. Land- und Siissw.-Conch. i. p. 46, t. 5. fig. 24°. 
Planorbis sumichrasti, Crosse & Fisch. Journ. de Conch. xxvii. p. 342 (1879)*; Miss. Scient. 
Mex., Mollusca, ii. p. 69, t. 33. figg. 6, 6 a-d®. 
Somewhat less compressed than P. cultratus, with the last whorl comparatively larger and the keel less 
acute. 
Hab. EF. Mexico: in the alluvial deposits on the beach (Strebel 1); Cacoprieto, Isthmus 
of Tehuantepec (Sumichrast 2°). 
Although Strebel’s measurements coincide exactly with those given by Fischer and 
Crosse for their P. culératus (from a specimen of unknown origin in the Sallé collection), 
the figures (corroborated by an example presented by Strebel to the Berlin Museum) 
show manifestly that his shell belongs to P. sumichrastt. 
Subgen. Tapuius. 
Taphius, H. & A. Adams, Gen. Moll. p. 202 (1858). 
Shell swollen and very concave on the right side, like that of Helisoma, but with 
the last whorl turning to the left near the aperture, which thus becomes very oblique. 
Known from the Andes of Peru (P. andecolus, dOrb.), and the Lake of Valencia, 
Venezuela (P. pronus, v. Mart.), as well as from Central America. 
19. Planorbis subpronus, sp. n. (Tab. XXI. fig. 15.) 
Testa subinflata, solidula, confertim striatula, obscure cornea, latere dextro profunde, sinistro mediocriter 
spiratim excavato, utraque excavatione subangulatim cincta, peripheria rotundata ; anfr. 34, celeriter 
crescentes, ultimus prope aperturam sensim descendens; apertura valde obliqua, semiovata, margine 
dextro leviter descendente, externo et sinistro bene arcuatis, columellari distincto, brevi, obliquo; paries 
aperturalis parum convexus, callo tenui textus. 
Diam. maj. 5, min. 4, alt. 2; apert. diam. 23, ampl. 2 millim. 
Hab. 8.E. Mzxico: Amatitan, State of Tabasco (Conradt, in Mus. Berol.). 
Allied to P. pronus, v. Mart. [Binnen-Mollusken v. Venezuela, p. 42, t. 2. fig. 5 
(1873)], but smaller, without spiral furrows, and with the last whorl less expanded at 
the aperture. In both species the width of the aperture does not exceed the absolute 
