402 MOLLUSCA. 
2. Ancylus papillaris, sp.n. (Tab. XXI. figg. 11, 11a, 12, 124.) 
Testa elliptica vel subovalis, depresse conica, microscopice striatula, tenuis, pallide cornea, subdiaphana, vertice 
valde obtuso, sulculo circumscripto, dextrorso, in + longitudinis teste posito. 
a. Long. 5:2, lat. 3°5, alt. 1°6 millim. (fig. 12). 
b 64, «644, 5, 29, ,, 14 = 4, = (fig. 11). 
Hab. N.W. Mexico: Rio Ameca, State of Jalisco (Richardson, Dec. 1884). 
This species belongs to the same subdivision of Ancylus as A. excentricus, which is 
characterized by having the summit of the shell turned to the right [not to the left, as 
in Ancylus (Velletia) lacustris, L.], this subdivision including also some Antillean and 
South-African forms. It varies somewhat in the outlines of the base, being either 
more narrowly elliptical (fig. 12) or more broadly oval (fig. 11); the radiating strie 
are very fine and not easily seen, and in some specimens they are present on the 
inner side only. ‘The summit is very obtuse and limited by one or even two 
concentric furrows from the other part of the shell, somewhat as in Spherium 
calyculatum, Drap. 
3. Ancylus excentricus. 
Ancylus excentricus, Morelet, Test. Noviss. ii. p. 17 (1851)*; Fisch. & Crosse, Miss. Scient. Mex., 
Mollusca, ii. p. 87, t. 80. figg. 16, 16a; Pilsbry, Proc. Acad. Phil. 1891, p. 3°. 
Velletia excentrica, Tate, Amer. Journ. Conch. v. p. 158%. 
Without radial sculpture, flat, attenuated in front ; apex pointed, in nearly ? of the length, much inclined to 
the right. Length 7, breadth 43 millim. 
Hab. Yucatan: Shkolak (feilprin ®). 
N. GuateMaLa: Lago de Itza, Peten (Morelet ! 2). 
E. Nicaragua: San Nicolas and San Agustin, district of Chontales, in pools and 
streams, on aquatic plants (Tate *). 
According to Pilsbry *, occurs also in Texas. 
Fischer and Crosse? state that the apex is 2 of the length, but in their figure it is 
nearly #. 
Var. biolleyi, n. 
Distinct from typical A. excentricus by being more elevated and compressed in its hinder part, and compara- 
tively a little narrower. Length 5-53, breadth 3, height 2 millim.; apex in ;%—4 of the length. Pale 
horn-coloured. 
Hab, CentTRaL Costa Rica: Rio Torres, on stones, and at San José, in irrigating-tubes 
(Biolley, 1891). 
Var. pittiert, 0. 
Very flat, broadly rounded behind ; apex depressed, somewhat blunt, in g of the length of the shell. More or 
less dark horn-coloured, in some specimens nearly black. Length 43, breadth 3, height 14 millim. 
Hab. S.W. Costa Rica: Ignacio, near San Domingo, and Rio de Los Platanales at the 
Golfo Dulce (Pitter). 
