10 MOLLUSCA. 
1. Megalomastoma (Tomocyclus) gealei. 
Tomocyclus gealei, Crosse & Fischer, in Journ. de Conch. xx. p. 77 (1872) '; Pfr. Monogr. Pneum. 
Vivent. iv. p. 189°; Fischer & Crosse, Miss. Scient. Mex., Mollusca, i. p. 118, t. 40. 
figg. 1-3 °. 
Hab. Cutapas (Boucard 12 8), 
N. GuareMaLa: woods between Tactic and Tamahu, Alta Vera Paz (Sarg?*); 
Polochic valley above Panzos and Senahu (Champion). 
2. Megalomastoma (Tomocyclus) simulacrum. 
Cyclostoma simulacrum, Morelet, Test. Noviss.i. p. 22°; Pfr.in Martini & Chemnitz, Syst. Conch.- 
Cab. ed. 2, Cyclostoma, no. 256, p. 267, t. 36. figg. 11, 12°. 
Megalomastoma simulacrum, Gray, Cat. Phaneropn. p. 92°; Pfr. Monogr. Pneum. Vivent. i. p. 181°; 
Sow. Thes. Conch. iii. t. 263. figg. 3, 4°; Tristr. P. Z.S. 1861, p. 282°. 
Megalomastoma (Tomocyclus) simulacrum, v. Mart. P. Z. 8. 1875, p. 649". 
Tomocyclus simulacrum, Crosse & Fischer, Journ. de Conch. xx. p. 76 (1872)°; Pfr. Monogr. 
Pneum. Vivent. iv. p. 140°; Fischer & Crosse, Miss. Scient. Mex., Mollusca, ii. p. 121, 
t. 40. fig. 9*°. 
Hab. N. Guatemata®®8%; woods near San Luis in Peten (Morelet11°); Coban 
(Salvin ™); between Tactic and Tamahu (Sarg}°); Vera Paz??4, 
Var. minus. 
Cyclostoma copanense, Sow. Thes. Conch. Suppl. i. p. 165, t. 31. figg. 310, 811%; Pfr. Monogr. 
Pneum. Vivent. i. p. 182”. 
Tomocyclus simulacrum, var. 8, Fischer & Crosse, loc. cit. t. 40. figg. 4, 5, 7, 8, 10”. 
Hab. N. Guaremata: Coban?! (Morelet 13); Alta Vera Paz’ (Bocourt!*); Senahu 
(Champion). 
Var. gracilius. 
Tomocyclus simulacrum, var. 6, Fischer & Crosse, loc. cit. t. 40. fig. 6 **. 
Hab. N. Guatemata: between Tactic and Tamahu, in the woods (Sarg 14). 
Fischer and Crosse (/. c. p. 120) insist on the specific differences between IV. gealei 
and MV. simulacrum, on the ground that in /. gealei the upper part of the peristome 
is never joined nor soldered to the preceding whorl; but we have an intermediate 
specimen collected at Senahu by Mr. Champion, distinctly costulated as M/. gealet, in 
which the upper edge of the peristome is really joined to the penultimate whorl. Of 
course this is only the consequence of a somewhat larger development of the broad 
peristome, and of less specific value than the sculpture of the whole shell. 
The var. gracilius approaches somewhat MW. guatemalense. 
The thread-like basal carina is more or less distinctly expressed in various specimens : 
in one, which was broken during life, there is no trace of it to be seen; it disappears in 
