PLANORBIS. 393 
9. Planorbis retusus. 
Planorbis retusus, Morelet, Test. Noviss. i. p. 17 (1849)*; Fisch. & Crosse, Miss. Scient. Mex., 
Mollusca, ii. p. 78, t. 82. figg. 10, 10 a-c?; Pilsbry, Proc. Acad, Phil. 1891, p. 822°. 
Planorbis planus, Clessin, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Limnziden, Pp. 222, 
t. 33. fig. 6%. 
Similar to the preceding, but flatter on the right side. 
Hab. Yucatan: Carmen Island (Morelet 12); Shkolak, between Merida and Valladolid 
(Heilprin®). 
This species is easily distinguishable by the flatness of the right side. Clessin had 
his specimen also from Morelet, but apparently without name and without indication 
‘of locality. 
10. Planorbis hondurasensis. 
Planorbis hondurasensis, Clessin, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Limneide, 
p. 164, t. 24. fig. 2 (1878)**. 
Hab. Honpuras: Santa Rosa (Hjalmarson '). 
CrntRAL Costa Rica: Rio Torres (Biolley). 
11. Planorbis tepicensis, sp. n. (Tab. XXI. fig. 14.) 
Testa tumidula, vix striatula, corneo-fusca, latere dextro medio profunde concavo, latere sinistro minus 
concavo, peripheria rotundata; anfr. 4, utrinque convexi, regulariter crescentes, ultimus ad aperturam 
3 diametri occupans ; apertura sat obliqua, intus albo-labiata, asymmetrice lunata, margine dextro leviter 
arcuato, margine sinistro ad insertionem magis arcuato et deinde oblique ascendente. 
Diam. maj. 6, min. 5, lat. 14; apert. diam. 23, ampl. 2 millim. 
Hab. N.W. Mexico: Tepic, State of Jalisco (Richardson). 
Although there is no striking peculiarity about this species, I cannot identify it 
with any one of those described by writers on American conchology. Its chief 
characters are the white lip of the aperture and the form of the sinistral margin, this 
last-mentioned peculiarity suggesting an affinity with the subgenus Helisoma ; but the 
plane of the aperture is much more oblique than in the species of that section of 
Planorbis. 
12. Planorbis petenensis. 
Planorbis petenensis, Morelet, Test. Noviss. ii. p. 15 (1851) *; Fisch. & Crosse, Miss. Scient. Mex., 
Mollusca, ii. p. 74, t. 33. figg. 5, 5 a-c*; Biolley, Moluscos Terr. y Fluv. de Costa Rica, 
p. 17°. 
* Clessin gives the locality as “ Sta. Maria, Honduras”; but on the label in Dunker’s collection it is 
clearly written “ Sta. Rosa.” His measurements, diam. 8, alt. 3 millim., are also incorrect (they should be 
diam. 5, alt. 2), according to a letter received from him in October 1898. Dunker’s largest specimen 
° 9 - 
measures diam. 7, alt. 23 millim. . 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, April 1899. 50 
