4 MOLLUSCA. 
Platystoma (Aperostoma) dysoni, Morch, in Malak. Blatt. vii. p. 66 (1860) °. 
Neocyclotus dysoni, Fischer & Crosse, Miss. Scient. Mex., Mollusca, ii. p. 164, t. 38. figg. 6-8, t. 39. 
figg. 9-12, t. 41. figg. 1, 2™. 
Cyclophorus translucidus, Tristr. P. Z.S. 1861, p. 232" (nec Sowerby). 
Cyclotus translucidus, Tate, in Am. Journ. Conch. v. p. 159”; Angas, P.Z.S8. 1879, p. 483" 
(nec Sowerby). 
Hab. 8.W. Mexico: Rio Grande in Oaxaca (Boucard: Fischer & Crosse 1°, t. 39. £.12 ; 
213 millim. in diameter); Istapa and Panistlahuaca in Oaxaca (Boucard: Fischer 
& Crosse}, t. 39. fige. 9,10; 20-23 millim. in diameter). 
CenTRAL Cutapas and Tapasco: Chiapas (Ghiesbreght ©: var. umbilico paullum 
latiore®), Teapa (H. H. Smith). 
Yucatan: Campeche (Dr. Berendt); Tabi in N.W. Yucatan (fF. D. G.; Febr. 1888: 
very small specimens, 16 millim.). (Tab. I. fig. 2.) 
N. Guatemata: Vera Paz (Salvin 11), Coban’, Tactic and Tamahu (Sarg 1°), Alta 
Vera Paz (Bocourt, Sarg: Fischer & Crosse’, t. 39. f£ 11; 30 millim. in 
diameter), Senahu and San Juan in Vera Paz (Champion). 
S.W. Guaremana, includ. §.W. Cutapas: Tapachula (Hége), San Isidro, Zapote 
(Champion: 19-21 millim.); Low country between Retalhuleu and the sea 
(Stoll). 
Honpuras (Dyson ! 2 3 4610), 
CentraL Nicaragua: Acoyapa (Belt; Dec. 1879); Chontales—forest-region, not 
uncommon, ascending the Pena Blanca to an elevation of 3000 feet, sparsely 
distributed in the savana-region (Tate 12), 
S.W. Costa Rica: Lepanta, Gulf of Nicoya (Gabb 18); Cervantes—only on hills, not 
common (Gab *); Punta Arenas?! ( Orsted). 
From an inspection of the original specimens, I may be allowed to state that the 
Vera Paz shell quoted as C. translucidus by Tristram " is C. dysoni and not the true 
C. translucidus, Sowerby ; the latter is a closely allied species, and chiefly differs from 
C. dysoni in the sculpture being distinctly more feeble. I, therefore, dare not include 
C. translucidus in the Central-American fauna, although Angas 1% and Tate !2 have also 
quoted it from within our limits. The true C. translucidus is from Venezuela. 
Colours of the living animal as in the preceding (Stoll). 
Var. n. ambiguus. 
Testa magis depressa, costulis minus undulosis. Diam. 28, alt. 16, apert. 11 millim. 
Hab. EB. Mexico, Soledad, between Cordova and Orizaba (Hége). 
Var. n affinis. 
Testa magis depressa, sculptura normali, colore castaneo. Diam. maj. 20, alt. 15, apert. 10 millim. (Tab. L. fig. 1.) 
Hab. 8. Panama, Bugaba (Champion). 
