460 | MOLLUSCA. 
another species, intermediate between P, indiorum and P. graphium. Fig. 10, on the 
contrary, has quite the appearance of a young shell, with the base of the last whorl 
more fully rounded and the base of the aperture apparently (?) projecting. I have not 
seen either of the specimens. 
17. Pachychilus corvinus. : 
Melania corvina, Morelet, Test. Noviss. i. p. 26 (1849) *; Hanley, Conch. Miscell., Melania, t. 2. 
fig. 16, and var. t. 8. fig. 257; Reeve, Conch. Icon. xii., Melania, t. 19. fig. 185 5°; Brot, 
in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Melaniaceen, p. 36, t. 5. fig. 1°. 
Pachycheilus corvinus, H. & A. Adams, Gen. Moll. i. p. 298, t. 31. figg. 7 a, 6 (operculum) ° ; 
Tristram, P. Z.S. 1861, p. 283°; Fisch. & Crosse, Miss. Scient. Mex., Moll. 11. p. 836, t. 52. 
figg. 7,7 a-c"; Pilsbry, Proc. Acad. Phil. 1892, p. 340° (nec Chenu, Manuel Conch. i. 
p. 289, fig. 1960). . 
Stoutly conical; last whorl rather convex, unicolorous, chestnut-brown; plane of the aperture concave; 
peristome thick, the interior with a dark brown marginal zone, the base rounded. Salvin’s specimen 
measures :—Long. 35, diam. 18 ; apert. long. 16 millim. 
Hab. 8... Mexico: Montafias de Poana 1, Tabasco (fovirosa ®). 
N. GuaTEMALA: smaller streams of the Department of Vera Paz (Morelet 14); Coban 
(Morelet, Bocourt"); Tactic (Bocourt*). 
W. Guatemata: Lake of Duefias (from O. Salvin’s first collection); in the stream of 
Santa Rosa, a tributary of the Rio Negro (Stol/). 
Var. lutescens. 
Melania corvina, Reeve, loc. cit. fig. 135 a’. 
Pachychilus corvinus, var. lutescens, Fisch. & Crosse, loc. cit. p. 336, t. 58. figg. 7, 7a. 
Shell pale yellowish-grey. 
Hab. N. Guatemata: Coban (Morelet '), 
Var. indifferens. (Tab. XXVII. figg. 10; 11, 11a, juv.) 
Pachychilus indifferens, Crosse & Fisch. Journ. de Conch. xxxix. p- 25 (1891) **; Miss, Scient. Mex., 
Moll. 1, p. 387, t. 50. figg. 8, 8 a-c”. 
Of smaller size; spire more conical and acuminated. 
Hab. N. Guatemata: Chiacam, near Lanquin, on the Cahabon River, an affluent of 
the Polochic (Champion). 
E. GuaTeMaLa: Rio Motagua (Bocourt !2), 
Among the specimens collected by Mr. Champion there are several very minute 
ones (figg. 11, 11 a), measuring 4-5 millim. only in length, with acute, not eroded, 
black-coloured apex and five to six whorls; they are without doubt very young, 
perhaps just hatched. 
