GAS TR O PODS. 
33i 
on the contrary, the number of laterals occasionally reaches live a side. They 
are curved and claw-like in some groups, but in others merely have serrated 
edges. Forty-two families are included in this section; but the limits of this 
work admit only of an account of some of the more important. The animals of 
one group are provided with shells, which either have a distinct, prolonged 
anterior canal, or else the aperture is more or less deeply notched at the base. In 
another group the mouth is entire, without notch or siphonal canal. Some have a 
retractile proboscis, like murices and whelks; others have a longer or shorter 
muzzle or rostrum, which is somewhat contractile. 
The first family is that of the tritons ( Tritonidce ), many of which possess large, 
handsome shells, exhibiting strengthening ridges (or former lips) at intervals upon 
the spire. The animal has a shortish foot, a large head projecting between the 
slender, pointed tentacles, supporting the eyes at the sides or at the base, and a 
horny operculum. Triton and Ranella are the two genera constituting this 
family. In the former, the large T. tritonis, the war-trumpet of the South-Sea 
islanders, is the typical kind. It attains more than a foot in length; and when 
the top of the spire is broken or ground ofF, a booming note can be produced. 
A similar species (T. nodiferus) lives in the Mediterranean, and was employed in 
the same way by the Romans. Most of the tritons are covered with a conspicuous 
periostracum, and in some cases this is beset with short hairs or bristles. The form 
of the shells is very variable in the different subgenera, but all exhibit the 
character of periodic ridges. The shells in the genus Ranella are very like Triton ; 
but the typical forms possess a posterior canal or sinus at the upper part of the 
aperture, which is not met with in the latter. The varices are mostly in two 
continuous series, one up each side of the spire. The species of this and the 
preceding genus are not very numerous—hardly two hundred altogether—and are 
chiefly inhabitants of warm climates. A few range as far north as Alaska and 
Japan ; others occur on the shores of Patagonia, the Cape of Good Hope, Amsterdam 
Island, and New Zea¬ 
land. Two species— 
T. nodiferus and T. 
cutaceus —have been 
occasionally obtained 
from the Channel 
Islands. Like Strom- 
bus, this group of 
molluscs appear to 
be great scavengers. 
M. Velain, when at 
Amsterdam Island, 
observed that the 
dead carcases of seals, 
left by fishermen on 
the rocks at low 
water, were literally covered with lobsters and Ranella at the following tide. In 
the helmet-shells, family Gassididce, the shells develop varices at intervals, like 
helmet-shell (Cassis glauca). 
