TWO DIVISIONS OF TKACHELIPODS. 297 
than the Coiichifer enclosed between the two 
valves of a Muscle or an Oyster shell. 
Lamarck has divided his Order of Tracheli- 
pods* into two great sections, viz. herbivorous 
and carnivorous; the carnivorous are also di- 
visible into two families of different office, the 
one attacking and destroying living bodies, the 
other eating dead bodies that have perished in 
the course of nature, or from accidental causes; 
after the manner of those species of predaceous 
beasts and birds, e. g. the Hyaenas and Vultures, 
which, by preference, live on carrion. The same 
principle of economy in nature, which causes 
the dead carcases of the hosts of terrestrial 
herbivorous animals to be accelerated in their 
decomposition, by forming the food of numerous 
carnivora, appears also to have been applied to 
the submarine inhabitants of the most ancient, 
as well as of the existing seas ; thus converting 
the death of one tribe into the nutriment and 
support of life in others. 
It is stated by Mr. Dillwyn, in a paper read 
before the Royal Society, June 1823, that Pliny 
has remarked, that the animal which was sup- 
* This name is derived from the position of the foot, or loco- 
motive apparatus, on the lower surface of the neck, or of the 
anterior part of the body. By means of this organ Trachelipods 
crawl like the common garden snail (Helix aspersa). This Helix 
offers also a familiar example of the manner in which they have 
the principal viscera packed within the spiral shell. 
