30 



Guide to the Mollusca. 



The Volutidae are much sought after by shell-collectors ; some 

 of them attain to a very large size.. They are found chiefly in the 

 warmer parts of the Atlantic; and Tndo-Paeific Oceans, and occur 

 in the greatest variety on the coasts of Australia. 



The Olirirfae are common in most tropical seas ; their shells 

 are remarkable for their beautiful polish and various patterns of 

 colouring. They burrow in sand in quest of bivalves for food. 

 and some species are said to have the power of swimming by 

 expanding the lobes of the foot. 



The Harpidae form a small, well-marked group. The animals 

 as well as the shells are brightly coloured. They have the 

 remarkable power of casting off a portion of the foot when 

 disturbed. The species are known from the Indo-Pacific Ocean, 

 the west coast of Central America, and West Africa. 



Fig. 21. 





^ rl 1/ 



The Common Whelk (Buccinum undatum). 

 a. siphon ; b. foot ; c. tentacles ; d. eyes ; e. operculum. 



The next family, the Pleurotomidae or Turridae, consists of very 

 numerous species, over a thousand living forms having been 

 discovered, and almost as many fossil species from Cretaceous 

 and Tertiary strata. 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. 



The " Auger-shells ' (Terebridae) have a great diversity of 

 external ornamentation. They are all elongate shells, with a deep 

 notch at the base of the aperture. 



The Conidae, or Cones, are found in all tropical seas. 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. They are all carni- 

 vorous, and live usually in shallow water among rocks and 

 coral-reefs. They possess a poison-gland, and several species are 

 recorded as having inflicted poisonous bites, often with serious 

 results. 



