THE MARSH GERITHIUM. 
325 
The color of the present species is slightly variable, but in the individual specimen the 
shell is marked with bold, zigzag streaks of white and pale buff, and the interior is pure white 
at the lip, changing to beautiful canary-yellow in the interior. The operculum is thick, hard, 
solid, and highly burnished, as if overlaid with glass ; its edge is regularly and finely grooved. 
Several allied shells are inhabitants of the fresh instead of the salt waters, and are known 
as Neritines. 
One of the most curious of these shells is the Spihed Neeitiha. The animal of the 
Neritina is not unlike that of the preceding genus, but there are one or two minute differences. 
The operculum is shelly, with a flexible border, and has some small teeth on its straight edge. 
All the Neritinse are globular in their general shape, darkly spotted or banded with black and 
purple, and covered with a polished bone-like epidermis. The color of the Spined Neritina is 
deep green-black on the exterior, and blackish-white within. The shell is thick and solid 
at the aperture, but becomes thinner towards the interior. 
The Ceowh Neeitiha. The color of this shell is gray, diversified with dark streaks. 
One species of this genus, the Eivee Neeitina {Neritina Jlumdtilis), is found in the rivers of 
Northern Europe. 
The curious shell represented in the accompanying illustration is an example of another 
family, that of the Clubs, or Cerithiadse. The shell of the Cerithites is spiral, more or less 
elongated, and the operculum is homy and spiral. The tentacles are placed rather far apart, 
and the eyes are set on very short footstalks. These creatures inhabit either marine, brackish, 
or fresh water. 
The Pelicah’s Foot, sometimes called Spout-shell, on account of the manner in which 
the aperture is lengthened into a kind of spout in front, has a rather elongated spire, and is 
considerably tuberculated on the exterior. As the 
animal approaches maturity, it adds fresh substance 
to the lip, until it bears some resemblance to the 
webbed foot of an aquatic bird. The animal has a 
short and rather abrupt muzzle, and moderately long, 
cylindrical tentacles, having the eyes set on protruber- 
ances near their base. Only three species of this genus 
seem to be at present known, but they have a wide 
range of locality, being spread over the greater part of 
the world, and found at various depths, sometimes 
being taken in a hundred fathoms of water. 
The color of the Pelican’s Foot is white, with a 
tinge of pink, and white inside. The shell is thickly 
and strongly made, and heavy in proportion to its 
weight. As may be seen by reference to our engraving, 
which is of natural size, it is not a large species, seldom 
measuring more than two inches in length. 
The GrEEAT Club-shell is considered a species belonging to the typical genus of the 
family. It is rather a large genus, containing at least one hundred known species, and 
ranging over the whole world. The largest species are, as is usually the case, to be found 
within the tropics. The shell is considerably elongated, and with many whorls, and the 
“ varices ” or marks of growth are partially visible on the exterior. The aperture is decidedly 
small when compared with the dimensions of the shell, and has a somewhat twisted canal in 
front. The outer lip is rather wide, and the inner is much thickened. 
One of these shells, the Maesh Ceeithium {Ceritliium palustre ), is supposed by some 
persons to produce the strange sub-aquatic musical sounds that exist in several Eastern lakes. 
A detailed account of these sounds, together with the reason for this conjecture, may be found 
in Sir J. E. Tennent’s “Natural History of Ceylon.” 
The color of the Great Club-shell is deep chocolate-brown on the exterior, slightly mottled 
with varying tints, and the interior is brown, but without the chocolate hue. 
PELICAN’S FOOT.— Aporrhais pes pelicani. 
