MEGALOMASTOMA. 11 
all near the aperture. The expansion of the outer peristome is quite even in some 
specimens, in others somewhat concave. The notch at the junction with the penulti- 
mate whorl is always narrower at its commencement and somewhat widened more 
behind, but in different degrees in various specimens; the outer lobe of the peristome 
reaches always the penultimate whorl and is more or less appressed to it; the inner 
(left) lobe remains free of it, although it comes very near in some examples. ‘The chief 
character of I. gealei lies in the sculpture of the shell, but this is also subject to some 
gradation according to the specimens; generally, the outer lobe of the peristome is free 
in MW. gealei, or touches only the penultimate whorl; the borders of the notch form a 
. perpendicular wall which reaches the basal keel, but this is also to be seen in some 
specimens of WM. simulacrum and not in all of VM. gealei. Finally, the separation of the 
last whorl from the suture near the aperture is more distinct in W/. gealez than it is in 
M. simulacrum. By comparing more specimens (three of M. gealei, seven of M. simu- 
lacrum), however, all these differences prove to be very gradual, so that the right of 
M. gealei as a distinct species appears rather contestable. 
3. Megalomastoma (Tomocyclus) guatemalense, 
Cyclostoma guatemalense, Pfr. P. Z.S. 1851, p. 245+; Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, 
Cyclostoma, no. 257, p. 267, t. 36. figg. 18, 147. 
Megalomastoma guatemalense, Pfr. Monogr. Pneum. Vivent. i. p. 182°; Gray, Cat. Phaneropn. 
p: 92°; Sow. Thes. Conch. iii. t. 263. fig. 6°. 
Tomocyclus guatemalensis, Crosse & Fischer, Journ. de Conch. xx. p. 76 (1872) °; Pfr. Monogr. 
Pneum. Vivent. iv. p. 1407; Fischer & Crosse, Miss. Scient. Mex., Mollusca, ii. p. 124, 
t. 40. figg. 11°. 
Hab. S.E. Mexico: San Martin Tuxtla, in the south of the State of Vera Cruz (Bou- 
card, Sallé ®). | 
N. GuateMaLa®’, Vera Paz?34 (mus. Cuming '). 
Megalomastoma guildingianum. 
Cyclostoma guildingianum, Pfr. in Zeitschr. f. Malak. 1851, p. 28; Martini & Chemnitz, Syst. 
Conch.-Cab. ed. 2, Cyclostoma, no. 218, p. 239, t. 31. figg. 25, 26. 
Megalomastoma guildingianum, Pfr. Monogr. Pneum. Vivent. i. p. 184; Gray, Cat. Phaneropn. 
p. 94. 
Locality unknown. Patel (Catalog. d. Conchyliensammlung, 1873, p. 120) cites 
Guatemala with a?; but nobody, so far as I know, has ever reported it thence. Very 
probably it belongs to one of the West-Indian islands. 
9* 
