438 MOLLUSCA. 
one suture to the other, or to the base of the shell, crossing the spiral lines, are here 
termed vertical plaits (plice verticales). 
Some of the species are used as food by the natives of Guatemala, according to 
Morelet and Bocourt (cf. Fischer and Crosse, loc. cit. p. 331) ; and this observation has 
been confirmed by Mr. Champion. ‘They are known to the Indians by the name of 
“jutes.” | 
The genus Pachychilus is confined to Central America and the northern parts of 
South America; in the West-Indian Islands it is represented in Cuba only, and there 
by smaller and somewhat aberrant forms, P. conicus, d’Orb., near P. schiedeanus, and 
P. (Potamanaz) brevis, Orb. It is clearly nearer to the genus Melania of the Old 
World than to the North-American Strepomatide. 
Fischer and Crosse have grouped the species under four subgenera, characterized by 
obvious features in the general shape of the shell; but there are several forms which 
are somewhat intermediate between the one and the other. Potamanaz, Pilsbry, may 
be added as another subgenus, distinguished by a difference in the form of the aperture 
and perhaps also in that of the operculum. 
‘The geographical distribution of the species in Mexico and Central America is 
given in the Table on the following pages. 
A. Subgen. GLYPTOMELANIA. 
Glyptomelania, Fischer & Crosse, Miss. Scient. Mex., Moll. ii. pp. 328, 351 (1892). 
Turrite, with more developed sculpture; outer margin of the aperture simple. Most 
of the species of rather large size. 
1. Pachychilus glaphyrus. | 
Melania immanis (Morelet, 1851), Brot, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Mela- 
niaceen, pp. 19-23, t. 2. figg. 1 a-g'. 
Pachychilus glaphyrus (Morelet, 1849), Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. pp. 350-357, 
t. 52. figg. 1, 2, & t. 53. figg. 1-4. 
Brot, Fischer and Crosse include all the forms of this very variable species under 
M. immanis or P. glaphyrus, the latter name having been first used by Morelet in 1849 
for a comparatively small, not very typical shell, though it is applicable also (yAaqupoc, 
in Greek, “carved”’) to the largest and most developed forms. 
The numerous varieties are known by different names, and they are here dealt with 
separately. 
a. Var. immanis. 
Melania immanis, Morelet, Test. Noviss. 1. p. 22 (1851)*; Reeve, Conch. Icon. xii., Melania 
t. 35. fig. 238 *. : : 
Melania immanis, a. typica, Brot, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Melaniaceen 
p- 20, t. 2. fig. la’. ° 
