646 SUPPLEMENT. 
Pachychilus chrysalis (p. 457). 
To the localities given, add :— 
Hab. Cuntrau Nicaraeua: Lake of Managua (Rothschuh, in Mus. Berol.). 
Pilsbry (Nautilus, xiii. p. 139) enumerates P. vulneratus, Crosse & Fisch., as a 
distinct species, found by Prof. Rovirosa in the Upper Puyacatengo River, near Teapa 
(S.E. Mexico) ; but he gives no other distinctive characters than a very widely extended 
erosion, leaving less than two whorls remaining. 
Pachychilus graphium (p. 461). 
To the localities given, add :— 
Hab. Yucatan (Godman, Febr. 1888). 
Pachychilus pilsbryi (p. 463). (Tab. XLIV. fig. 8.) 
Pachychilus (Potamanaz) rovirosai, Fischer & Crosse, Miss. Scient. Mex., Moll. ii. p. 668, t. 71. 
fig. 12° (apparently copied from Pilsbry’). 
To the locality given, add :— 
Hab. {8.E. Mexico:] Santa Gertrudis in Tabasco, at the Usumacinta River, amongst 
gravel on the dry bank of the river (Berendt, in Mus. Hamburq.). 
Dr. Berendt’s specimen, here figured, is of somewhat more slender form than Pilsbry’s 
type, measuring 17 millim. in length, diam. 10, aperture 7 in length and 64 in breadth, 
including the columellar margin. It has nine distinctly prominent, brownish-black, 
spiral ridges on the last whorl, and five on the visible part of the penultimate whorl, 
these contrasting in colour with the pale grey interstices, the upper two on each whorl 
being slightly nodulose ; between the second and third ridges a much narrower, pale 
reddish one is intercalated, and there is a similar one at the base below the ninth. 
Pilsbry1 states that the spiral lire are somewhat alternating in size. It is to be 
regretted that the operculum is still unknown. The broad columellar margin, the 
rounded basal margin of the aperture, the spiral sculpture, and the solidity of the 
shell give P. pilsbryi the general aspect of a species of the submarine genus Littorina. 
SEMISINUS (p. 464). 
2. Semisinus maculatus. (Hemisinus maculatus, Tab. XLIV. fig. 7.) 
Melanopsis maculata, Lea, Trans. Am. Phil. Soc. v. (=Obs. Unionid. i.) p. 194, t. 19. fig. 75 (1832) '. 
Melania osculatii, Ant. Villa, Notizie intorno al genere Melania, in Atti dell’ Accad. fisico-medico- 
statistica di Milano, no. 2, p. 8 (1855) *. 
Hemisinus osculatii, Reeve, Conch. Icon. xi., Hemisinus, t. 8. fig. 10 (1860) °; Brot, in Martini & 
Chemnitz, Syst. Conch.-Cab. ed. 2, Melaniaceen, p. 379, t. 8. figg. 7 and 8, 8.a,b'. 
Hemisinus binneyi, Tryon, Am. Journ. of Conch. ii. p. 8, t. 2. fig. 8°. 
Shell ovato-oblong, truncated above, moderately attenuated below, smooth, greenish-brown, with spiral rows 
of darker brown square spots, in about 10 spiral rows on the last whorl, the upper ones by pairs nearer 
