The next family, the “Slit-lips” (_Pleurotomatidæ_), 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. [Sidenote: Cases 87–89.] The “Auger-shells” (_Terebridæ_), like the Cones, present a great similarity in form, but, unlike them, have a great diversity of “_sculpture_” 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. [Illustration: Fig. 14. The “Glory-of-the-Sea” Cone (_Conus gloria-maris_). Case 94. (From the Philippine Islands.) ] [Sidenote: Cases 89–94.] The _Conidæ_, or Cones, form one of the most beautiful portions of the collection of Shells. This family, of which between 400 and 500 distinct kinds are known, is a great favourite with collectors on account of the brilliant colours and various patterns of the shells. Some, owing to their beauty and rarity, have been sold at very high prices, as much as £50 having been paid for a single shell. The Cones are found in all tropical seas, but are rare in cold or temperate latitudes. None are met with on our own shores, one species alone being known from the Mediterranean. They occur fossil in the Chalk and Tertiary strata. These animals are all carnivorous, and live usually in shallow water among rocks and coral-reefs. Some of them are said to bite when handled, and to be dangerously poisonous, the bite in some instances having been all but fatal. [Sidenote: Case 94.]