Occasional Papers of the Museum of Zoology 45 
not adnate to the body whorl. If this process should be con- 
tinued long enough, I have no doubt it would result in the 
complete freedom of the peristomal margin. 
The shells of the form mexicanum are more variable in 
appearance than are those of salleanum. ‘The growth-wrinkles 
of the former are quite irregular, and the epidermis is usually 
eroded toward the tip, which may be somewhat chalky in 
appearance. Specimens measure: 
Altitude Greatest diameter Height aperture Diameter aperture 
Smallest 14.5 145 (21) 66 (9.5) 69 (10) 
Fig. 10 17.0 135 (23) 65 (11) 65 (11) 
Fig. 11 15.0 149 (23) 65 (10) 68 (10.5) 
Fig. 12 15.0 150 (22.5) 67 (10) 70 (10.5) 
Part III. ZoNrITiIpDAE AND HELICIDAE 
ZONITIDAE 
Guppya gundlachi (Pfeiffer) (1840)—One hundred three 
specimens; on ground among humus and decaying leaves in 
the lowland forests (H, I, a); and a few feet above ground, 
on young palms in the lowland forests (H, I, b) ; on elephant- 
ears along Arroyo Hueyapam (H, II, a), and on cacti in the 
savannah brush (H, III, b). Apparently, it is a ground spe- 
cies, which moves up into the lower vegetation in the wet 
season. 
As the dried animals were still in some of the shells, two 
preparations of the jaw and radula were made and examined. 
The jaw (fig. 3) is quite similar in structure to that of Huconu- 
lus, but has a more nearly semicircular outline. The formula 
of the radula (fig. 1) may be expressed: 
I 5 242 I 
C—;L—;M—-+ — + —;3 or 27-5-1-5-27. 
$ 3 3 + I 
The central has broader and shorter cusps than Euconulus. 
The first four laterals are practically the same shape as the 
central; in fact, I could not determine which was the central 
