RISSOID Aa. 269 
Bueesta, Paladilhe. 
Distr.—B. Bourguignati, Palad. (1xxiii, 69). 
Shell turreted, conic, with revolving grooves, and longitudinal 
costulz ; aperture ovate, slightly angular below and above, outer 
lip rounded ; columella straight, compressed, not callous, slightly 
truncate at the base ; imperforate. Operculum unknown. Micro- 
scopic. France. 
Barikauia, Martens. 
Syn.—Limnorea, Leucosia, Dybowski. 
Distr.—20 sp. Lake Baikal; Colorado Desert (California). 
A. Angarensis, Gerst. (1xxiii, T0). 
Shell turriculated, whorls usually convex, spire lengthened ; 
aperture slightly angulated below. Operculum corneous, as in 
Hydrobia. 
LIOBAIKALIA, Martens. Whorls of the spire not in contact. 
Form resembling Liogyrus in Valvatide. B. Stiedie, Dyb. 
(Ixxiii, 71). 
GODLEWSKIA, Crosse and Fischer. Shell having varices. JB. 
turriformis, Dyb. (1xxiii, 72). 
TRACHYBAIKALIA, Martens, 1879. Shell Melaniform, longitu- 
dinally costate. B. carinato-costata, Dybowski (1xxxiii, 73). 
With this group may also be united as a subgenus :— 
TRYONIA, Stimpson. Shell perforate, elongated, turreted, subu- 
late, acute at the summit and rather pointed at the base ; surface 
longitudinally ribbed, plicated or cancellated, not spinose; whorls 
numerous, more or less shouldered; aperture small, oblique, 
rhombovate, somewhat pointed, effuse and sinuated at the base ; 
outer lip thin and sharp, projecting below, inner lip appressed to 
the whorl above, peritreme continuous. Operculum and animal 
unknown. Dist7.—Fresh water, semi-fossilized. Colorado Desert, 
Southern California. B. clathrata, Stimpson (1xxii, 74). 
DYBOWSKIA, Dall., 1876. Ribs covered with a ciliated epidermis. 
B. ciliata, Dybowski. Lake Baikal. 
PoraMoPpyRGus, Stimpson. 
Distr.—F resh water, New Zealand, Cuba. P. Candeana,dOrb. 
(Ixxiii, 75). 
Shell ovate-conic, imperforate, apex acute, whorls coronated 
with spines; aperture ovate, outer lip acute. Operculum cor- 
neous. Rostrum moderate, tentacles very long, slender, tapering 
and pointed; eyes on very prominent tubercles ; foot rather short, 
broadest in front and strongly auriculated. 
Pyraipium, Tournouer. 
Distr.—Tertiary ; Austria. P. Tournouert, Neum. (1xxiii, 76). 
Shell small, pyramidal or turreted; aperture ovately pyriform, 
