436 MOLLUSCA. 
Ancey found only one specimen among a number of A. wrighti, and says that it is 
very like (“ tout-a-fait”) the Hydrobia ulve of the coasts of France; if so, one might 
be tempted to suggest that it was really an example of that species which by some 
accident had been placed among the Central-American shells in his collection. 
13. Amnicola (2?) melanioides, sp. n. (Tab. XXII. fig. 8.) 
Testa oblongo-lanceolata, imperforata, levis, nitidula, periostraco olivaceo-nigricante tecta, apice obtuso ; 
anfr. 4-5, planiusculi, regulariter crescentes, sutura superficiali, ultimus oblongo-ovatus, basi leviter 
convexus, a dorso visus 4 fere longitudinis teste occupans ; apertura paulum obliqua, anguste ovata, 
superne acutangula, margine externo tenui, vix arcuato, margine basali valde arcuato, margine columellari 
valde incrassato, cerulescente, sensim in callum parietalem transeunte, fauce cerulescente. 
Long. 62, diam. 24; apert. long. 3, diam. 1? millim. 
Hab. S.W. Costa Rica; Golfo Dulce, Rio de Los Platanales (Pitter, 1896). 
Var. tenuis,n. (Tab. XXII. fig. 9.) 
Testa magis tenui, olivaceo-fusca; anfr. 6, margine columeilari non incrassato, fauce albida. 
a. Long. 43, diam. 13; apert. long. vix 2, diam. 13 millim. 
b. ” 64; ” 23 5 ” 23, ” 13 ” 
Hab. S.W. Costa Rica: in a small stream running into the Rio Boto at Golfo Dulce 
(Pittier, March 1896: form a); marshes of Seripe, 5 metres above the sea, ou 
aquatic plants (Pittier, April 1892: form 6, often somewhat incrusted). 
As neither operculum nor radula could be examined, the generic position of this 
shell remains rather doubtful. 
TRYONTA. 
Tryonia, Stimpson, Amer. Journ. of Conch. i. p.54 (1865) ; Researches on Hydrobiine (Smithson. 
Misc. Coll. no. 201), p. 48 (1865). 
Shell turrite, longitudinally ribbed, not spinous; aperture oval, spreading at the 
base; peristome simple, continuous, appressed on the columellar side. Operculum and 
radula unknown. 
Geographical distribution, California and Central America. 
1. Tryonia exigua. 
Melania exigua, Morelet, Test. Noviss. 1. p. 23 (1851) '; Reeve, Conch. Icon. xii., Melania, t. 58. 
fig. 460°; Brot, Matériaux étud. fam. Mélaniens, p. 42 (1862)* (nec M. exigua, Conrad, 
1855,= Tryonia protea, A. Gould). 
Tryonia exigua, Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. p. 275, t. 50. figg. 2, 2a, b'. 
Melania minuta, Brot. loc. cit. p. 43°. 
Nearly imperforate ; whorls 6-73, not very convex, angularly shouldered at the suture, with strong, smooth 
longitudinal ribs, about 12-13 on the last whorl. 
Long. 7-84, diam. 3; apert. long. 2-23, diam. 13-2 millim. 
Hab. N. Guatemana: Lake Itza, Peten (Morelet 1-5), 
Only known in a subfossil state. 
See also Amnicola seemanni, page 435. 
