Ad. Mr. Rh. J. L. Guppy on the Terrestrial and 
those of a fish; they are placed on stout pedicels joimed to the 
outer and hinder side of the tentacles, which are acutely pointed 
and of moderate length. The jaws are large, smooth, and almost 
shelly. The lingual teeth are 3.1.8: central broad, sub- 
quadrate, with a strong apical point, on each side of which are 
two smaller dentations ; first lateral broad, obtusely pointed, 
with a dentation on the inner edge; two outer laterals similar, 
simply claw-shaped. The dental membrane is supported on 
two large triangular cartilages, to which are attached strong 
muscles. 
This species inhabits the larger rivers and swamps, burying 
itself in the mud during the dry season. | 
Var. purpurascens (A. purpurascens, Guppy, Ann. & Mag. 
Nat. Hist. ser. 3. vol. xiv. p. 243). 1 described this form as a 
distinct species, but I have since seen reason to believe it only 
a variety of A. urceus. 
Ampullaria effusa, Chemn. (A. glauca, Linn.) 
This shell is rather variable, both as to colour and shape. I 
have described a variety, for which I propose the name conica, 
in the ‘ Annals’ (doc. cit.), and I have also there described the 
eggs and young shell of A. effusa. Another variety of A. effusa 
I propose to distinguish by the name ¢ristis. In this variety 
the spire is rather more elevated than in the type, the peristome 
more prominent, and the colour-bands are either altogether ab- 
sent or externally indistinct, the shell being of a dark horn- 
colour. These varieties would probably be regarded as distinct 
species by many naturalists; but my acquaintance with the 
habits of the species enables me to affirm that the differences 
are not specific. 
This species, like A. wrceus, buries itself during the continu- 
ance of drought. It can exist for months in a torpid state. 
The typical form is found in rapid streams, while the varieties 
conica and tristis occur in slow-running water and in ponds, 
I think it probable that A. crocostoma, Phil., a Venezuelan 
shell, is only another variety of this species; and there may be 
other forms which ought in strictness to come under the same 
specific appellation. 
Marisa, Gray. 
Marisa cornu-arietis, Linn., sp. 
M. Knorrii, Phil.; Ceratodes fasciatus, Guilding. 
The animal is grey, mottled and streaked with brown and 
black. The muzzle is produced into two acute tentaculiform 
lobes. The left siphon, as well as the right one, is rudimentary 
