452 -MOLLUSCA. 
a. Long. 63, diam. 17 (19); apert. long. 17, diam, 11 millim. Anfr. superst. 10-11. 
b. ” 49, 9 19 5 ” 20, 9 11 9 ” 5. 
a. One of Tristram’s specimens measured by myself; 6. Fischer and Crosse’s measurements. 
Hab. N. Guatemaua; Rio de la Pasion, a tributary of the Usumacinta, in the Depart- 
ment of Alta Vera Paz (Salvin 11718). 
E. GuaTeMALA: in small streams near the Lake of Yzabal (Bocourt *}). 
W. Guatemata: Lake of Amatitlan (Bocourt 41°). 
Athough the localities are different and the measurements do not accord, yet on 
comparing Canon Tristram’s specimens, kindly lent me by their possessor, with the 
figure given by Fischer and Crosse, I find they must be referred to the same variety of 
P. largillierti. The shell figured by the French authors is an older one and has lost 
more of its whorls than that measured by Canon Tristram and myself; it is thus abso- 
lutely shorter, but larger in periphery and in aperture. In one of Tristram’s specimens 
spiral ridges are also present on the upper half of the last whorl, but not in the 
preceding ones; in the other example only at the base. ~ 
Var. stolli,n. (Tab. XXVI. figg. 5-9.) 
Distinctly more cylindrical and of smaller size, ordinarily broadly truncated above, 4—5 whorls only remaining ; 
these are feebly convex, with very fine spiral stria, and more distinct, but irregular, scattered, vertical 
strie, some of which are more prominent, ridge-like ; suture distinctly impressed. Last whorl not more 
ventricose than the preceding, its largest diameter somewhat below the half of its height; base with 
several more or less distinctly prominent spiral ridges. Aperture comparatively small, scarcely produced 
below ; columellar margin thickened, well arcuated. Surface of the shell dark greenish-brown or blackish, 
somewhat shining; columellar margin pale bluish, interior of the aperture dull greyish. 
a. Long. 30, diam. 13; apert. long. 11, diam. 7 millim. 
b 6, «626, 4, 125 ” 10, 4 7 4 
Hab. W. Guatemata: on the north-western slope of the Cordillera, in the environs 
of Retalhuleu (Séol/). 
In its general shape this form somewhat resembles P. liebmanni, var. gassiesi. At 
first sight I was inclined to treat it as a distinct species; but the small size, the great 
decollation, and the repeated traces of stoppages of growth in the last whorl give it 
the appearance of a somewhat stunted form living under unfavourable conditions, 
analogous to the var. ¢rrigua of Melania libertina, Gould, of J apan. 
Melania murrea, Reeve, Conch. Icon, xii., Melania, t. 20. figg. 138 a,b (1860); Brot, 
in Martini and Chemnitz, Syst. Conch.-Cab. ed. 2, Melaniaceen, p. 30 (part.), t. 3. fig. 7b 
(young), seems to be nearest this species, only the whorls are more even, the upper 
ones angulated near the suture, the last less rounded. Its locality is quite uncertain: 
Reeve merely says that it is “‘ of the Central-American type.” 
