16 SHELL GALLERY. 



and live usually in shallow water among rocks and coral-reefs. 

 Some of them are said to bite when handled, and to be danger- 

 ously poisonous, the bite in some instances having been all but 

 fatal. 



The " Auger-shells " (Terebrldce) , like the Cones, present a great 

 similarity in form, but, unlike them, have a great diversity of "sculp- 

 ture" or external ornamentation. They are all elongate shells, with a 

 deep notch at the base of the aperture. Owing to the length and 

 comparative solidity of the shells, the animals of many of the 

 species do not carry their shelly structures on their backs, like 

 most other species, but drag them along the sandy sea-bottom. 



The next family, the "Slit-lips" (Pleurotomatida), consists of 

 very numerous species, over a thousand living forms having been 

 discovered, and almost as many fossil species from Cretaceous 

 and Tertiary strata have been described. The typical forms are 

 characterized by a slit in the outer side (lip) of the aperture. 

 Species of Pleurotoma are found in every sea, although most 

 abundant in the tropics, and, although so numerous in species, the 

 number of specimens is small in comparison with some other 

 genera. 



The family of Muricidce, or "Rock-shells," is another extensive 

 group, containing many very handsome and peculiar forms. The 

 animals of this family have a long proboscis, at the end of which is 

 the spiny tongue (odontophore), and which is retractile within the 

 body. The true Murices produce at intervals ribs or varices, 

 which in some species are ornamented with long spines or foliations, 

 and which indicate periods of growth, but of what duration we do 

 not know. They are all carnivorous, feeding chiefly on other Mol- 

 lusca, boring through the shells of bivalves with their spiny tongue, 

 and slowly devouring the unfortunate inhabitant piecemeal. From 

 certain species of Murex (M. brandaris, &c.) , found in the Medi- 

 terranean, the ancients manufactured the celebrated Tyrian purple 

 dye. 



The family of Buccinidce also contains a very large and various 

 assemblage of forms. Among them may be mentioned the Whelks 

 [Buccinum) and the "Purples" {Purpura), found between tide- 

 marks all over the world. Magilus is found among coral-reefs in 

 tropical seas, and has the remarkable habit of lengthening the 



