POTAMIDES. 569 
1833), and mentions in a footnote some recent Species which would come into the same 
genus, as P. palustris, L., and P. muricatus, Brongn. (=/fuscatus, Linn.). His fossil 
P. lamarcki is very near P. fuscatus, and so I think the name Potamides, in its 
pestricted sense, must be applied to the subdivision which contains the West-A frican 
forms P. fuscatus and P. radula, e. g. the division called Tympanotonos (Klein) by 
Morch, H. & A. Adams, Reeve, P. Fischer, &c. Zympanotonos of Klein (1753) 
prcodes various Cerithiide, but the shell figured by Klein himself to illustrate it is 
Vibex fuscus, Mill. (= Claviger matoni, Brot.), placed by most recent authors among 
the Melaniide. P. ebeninus is the type of Pyrazus, Montfort, and it may be placed 
near P. palustris; but for P. pacificus a new subgeneric name is wanted. The form of 
its operculum, however, is not known (at least it is not known to me), and therefore I 
am not quite satisfied whether P. pacificus really belongs to Potamides or to Verithium, 
near C. uncinatum (Gmel.), as Kobelt suggests. Its habit of living in mangrove- 
thickets, however, suggests that it is nearest allied to Potamides. 
I. CEritHipEa, Swains. 
1. Potamides varicosus. 
a. validus, 
Cerithium varicosum (Val.), Kiener, Iconogr. p. 94, t. 30. fig. 2 (1842)’; Deshayes, in Lamarck’s 
Hist. Nat. d’Anim. sans Vert. éd. 2, ix. p. 321°; d’Orbigny, Voy. Am. mér., Moll. p. 448°; 
Sowerby, Thes. Conch. ii. p. 887 (part.), t. 185. fig. 280*; Kobelt, in Martini & Chemnitz, 
Syst. Conch.-Cab. ed. 2, Cerithium, p. 58, t. 12. figg. 2, 3°. 
Cerithidea varicosa, Reeve, Conch. Icon. xv., Cerithidea, t. 3. fig. 19a°; Carpenter, Report Moll. 
W. Coast of N. Am. pp. 230, 272, 325°; Moll. of W. N. Am. pp. 24, 186 (1872) ‘; 
Troschel, Gebiss d. Schnecken, i. p. 147, t. 12. fig. 3 (radula) °. 
Cerithium validum, C. B. Adams, Ann. Lyc. Nat. Hist. N. York, v. p. 881 (1852) °°. 
Cerithidea valida, Morch, Malak. Blatt. vii. p. 80 (1861) **. 
Cerithium fortiusculum, Bayle, Journ. de Conch. xxviii. p. 250 (1880) ”. 
Potamides montagnei (part.), Tryon, Man. Conch. ix. p. 161, t. 53. fig. 58 (copied from Reeve) *. 
Vertical ribs rather straight and composed of strong tubercles connected by a feeble ridge; on the last whorl 
the ribs diminish in number in comparison with those of the preceding whorls, only 12-15, in somewhat 
smaller specimens (full-grown ?) 18. Varices usually yellowish-brown behind, white in front. 
Long. 35-41, diam. (incl. peristom.) 16-21 millim. 
Hab. W. Nicaracua: Realejos, at roots of mangroves (Cuming * °). 
W. Costa Rica: Punta Arenas, in the Gulf of Nicoya (Ersted ! & C. Hoffmann, in 
Mus. Berol.). 
S. Panama: Panama (Jewett 8), half buried in muddy sand, under bushes, at high- 
water mark (C. B. Adams !°). 
Cotompta: Tumaco (Hopke, in Mus. Berol.). 
Ecuapor: Guayaquil, in brackish water of the river of that name, very common 
(d’ Orbigny *). 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, November 1900. "9 
