PLANORBIS. 389 
Var. chiapasensis. 
Planorbis ancylostomus, var. chiapasensis, Fisch. & Crosse, Miss. Scient. Mex., Mollusca, ii. p. 63, 
t. 84. figg. 5, 54,b*. 
Very small: diam. maj. 103, alt. 5 millim.; left side with a distinct spiral angle; aperture less 
asymmetrical, 
Hab. S.E. Mexico: Chiapas (Sallé 26). 
This form has very much the appearance of a not full-grown shell, but it is more 
compressed than young shells of the typical P. caribeus of the same diameter. 
P. caribeus* is in most respects very near P. tenuis, but at first sight very distinct 
from it by the more gradual increase of the whorls, the more compressed form, and 
the greater space occupied by the penultimate whorl, as well as by the less conspicuous 
difference between the two sides of the shell. All these differences, however, are due 
to a later stage of growth, appearing more distinctly in the last whorls, as in young 
shells of about 10 millim. in diameter, and with four whorls, the deep spiral exca- 
vation of the right side and the flat tray-like excavation of the left side are essentially 
alike in both species (figg. 7, 9), and the only real difference between them is in the 
* As regards the name to be used for this species and what localities to quote, there are several difficulties. 
(1) Do the Cuban and Mexican specimens belong to one and the same species, or are they distinct? Several 
authors, including myself, formerly separated them, because the figure given by Dunker®*, from a Cuban 
specimen, exhibits a less asymmetrical form than the full-grown Mexican ones; nevertheless, in d’Orbigny’s 
original figure of P. caribeus the aperture is very asymmetrical, and I find on examining the Cuban shells 
given to the Berlin Museum by J. Gundlach that they have a triangular or irregularly pentangular aperture 
like that of the Mexican examples, and exhibit no other constant difference ; therefore I prefer now to follow 
d’Orbigny * and Dunker* in uniting them. (2) P. capillaris, Beck (1837), has never been defined ; it can be 
recognized only by the place which the author has assigned to it near P. banaticus and P. coromandelicus, and 
by a specimen in Dunker’s collection from Steenstrup bearing the name P. captllaris. P. tumidus, L. Pfeiffer ? 
(1839), also undefined, is said to resemble P. fragilis, a species undescribed at that time; the first published 
description and figure of P. tumidus, that by Dunker *, is clearly subsequent to that of P. caribeus, d’Orb.”, as 
Dunker himself quotes d’Orbigny’s name and publication. Both names, P. tumidus, Dunk., and P. caribeus, 
- @Orb., were applied originally to Cuban specimens, but d’Orbigny 0, as well as Dunker’, includes also 
Mexican shells under P. caribeus. If the two are regarded as one species, P. caribeus has priority, and the 
name P. twmidus would be best dropped. If necessary, the Mexican shell could always be separated from the 
Cuban one under the name P. ancylostomus, Cr. & Fisch.*. (3) It is doubtful whether this species really 
inhabits Central Mexico: in a former paper® I have quoted the city of Mexico as a locality for it, on the 
authority of Uhde, as there are two blackish incrusted specimens in the Berlin Museum so labelled by him— 
they belong to the var. minor, which is rather widely distributed ; but as neither Strebel, nor Boucard, nor 
Heilprin has found this species in the environs of the city of Mexico, this locality requires confirmation. 
Dunker ® also adds to its distribution ‘‘ Vamba (Hegewisch) ” ; this place is said to be in the State of Vera Cruz 
by Fischer and Crosse, but in the label in Dunker’s collection it is ascribed to the western shore-regions of 
Mexico. Pilsbry *™ gives, as distinct species, P. tumidus, from Vera Cruz and Orizaba, and P. caribeus, from 
Yucatan ; one of these possibly belongs to our var. minor. 
