"The species are covered with an epidermis, sometimes very thick; the spire has various degrees of elevation, sometimes almost flat; the operculum very small and horny. They are natives of southern and tropical seas: the animal is carnivorous: found in sandy mud, at various depths of the ocean. The species are very numerous--Lamarck makes 181 recent. Some new species have lately been discovered. Many of the cones are very beautiful, both in shape and colour, and the genus has been always in estimation among collectors. The _gloria-maris_, _cedonulli_, _ammiralis_, and some others, have been sold at very high prices, and some of the finest of these are now in England. "Lamarck makes two divisions: in the first is comprehended the species with coronated spires; the second those with simple spires; the latter division contains far the greater number. "Fossil cones occur, in London clay and crag, in England. "No recent species are found upon our own coasts. "_Conus Hebræus_, the Hebrew-cone, is easily known: (Plate 6:) it has a white ground, and square black markings. "_Conus virgo_ is white, with a purple base. [Sidenote: CONUS.] "_C. marmoreus_ is a fine shell. Numerous species are within reach of your purses, and I do not doubt that you will soon acquire a good collection at a moderate price. You, Charles, will find more pleasure in a cone than in a top; and Lucy, who never found much pleasure in toys except in taking them to pieces, has always a ready sixpence either for a poor neighbour in distress, or for some harmless pleasure. "We have yet two more orders of _Mollusca_ to notice, the _Cephalopoda_ and the _Heteropoda_. "At our next lesson I shall mention the genera that are most likely to come under your observation, either fossil or recent." CHAPTER XII. [Sidenote: ARGONAUTA. NAUTILUS.] "So many families of the fourth order, _Cephalopoda_, are found only in a fossil state, and which you will not easily meet with, that I shall not consider it needful to give you the whole catalogue," observed Mr. Elliot to his young pupils at the beginning of the next lesson. "But we are exceedingly interested about fossils," replied Charles; "pray do not pass any species that we may be likely to find." "And I," said Lucy, "have much wished to ask whether the _snake-stone_ ever was a shell? it is something like a _Planorbis_, but heavy and imperfect." "I will answer your question presently," said her father. "Tell me what genera remain to be noticed among the univalves of Linnæus?" "_Argonauta_ and _Nautilus_," was the ready reply. "The animals inhabiting these shells are _Cephalopoda_. The word indicates the position of the feet, or more properly _arms_ of the animal, which are ranged round the head like a crown. The body is thick and fleshy, contained in a kind of bag, whence the head issues, surrounded by these arms, which vary in different genera. [Sidenote: CUTTLE-FISH. BELEMNITE. SPIRULA.]