INTRODUCTIO. 7 
5. Genus Alexia Leach. Foot simple beneath, without 
a transverse groove. — Shell oblong-ovate, imperforate, smooth ; 
spire acuminate; aperture elongate, oval; inner lip 3— 5 plait- 
ed, the posterior plait small; outer hp with the margin re- 
flexed, thickened or dentate internally. 
6. Genus Carychium Müller. Foot not transversely di- 
vided beneath. — Shell sub-cylindrical, thin, conie, ovate; 
spire elevated, whorls few, rounded; aperture small, oblong, 
longitudinal; inner hp straight, with a single fold; outer lp 
thickened and rather reflexed. 
II. Sub-fam. Melampinae. Animal amphibious, or living 
in brackish water. "Tentacles developed, eyes at their inner 
bases. — Shell with the inner lip plieafe; outer lip straight 
and acute. 
1. Genus Melampus Montf. Foot bifid posteriorly. — 
Shell ovato-conical; spire short, obtuse; aperture narrow, 
linear; inner lip with several transverse folds; outer lip acute, 
internally plicate. 
8. Genus Tralia Gray. Foot posteriorly acute, entire. 
— Shell ovate, smooth ; spire elevated; aperture narrow, linear, 
dilated anteriorly; inner lip usually with three oblique plaits; 
outer lip acute, sinuated posteriorly, internally with one or 
more transverse elevated rndges. 
Sub-gen. Pira H. et A. Adams. Shell ovate, smooth; 
spire elevated; aperture narrow, linear; columella usually with 
three anterior plaits; outer lip internally with numerous, ele- 
vated, transverse ridges. 
Sub-gen. Tifata H. et A. Adams. Shell subglobose; 
aperture narrow, contracted; inner lip with two spiral, ele- 
vated, lamellar plaits at the fore part; outer lip internally 
lirate. 
Sub-gen. Signia H. et A. Adams. Shell ovate, whorls 
granular, or decussated with longitudinal and transverse groo- 
ves; outer lip internally with a single, transverse, elevated rib. 
Sub-gen. Persa H. et A. Adams. Shell ovate; spire 
obtuse, whorls longitudinally ribbed and transversely striated ; 
aperture wide; outer lip acute, simple internally. 
9. Genus Ophicardelus Beck. Shell ovate-oblong, um- 
bilieated, smooth; spire elevated, sub-conic; aperture oval; 
inner lip anteriorly dilated and reflexed, with two plaits at 
the fore part, the posterior spiral forming an elevated ridge 
round the umbilical region; outer lip thin, simple. 
10. Genus Laimodonta Nuttall. | Shell oblong -ovate, 
imperforate, thin, transversely striated; spire elevated, conic; 
aperture oval; inner lip with three plaits, the anterior small; 
