X. — MOLLUSCA. 79 



The remaining Familes and Orders have not yet been finally 

 arranged in the Cases, and, in the meantime, a full description 

 of them is not given, but the following list of the contents of the 

 cases will be of interest : — 



Case I. — Besides the Families already described, this case 

 contains the Volutes ( Volutidce) a group of shells very 

 much sought after by shell-collectors ; the greatest variety 

 of them are found in Australia. 



Case II. — The Trumpet Shells (^Tritonidcti) have varices or 

 strengthening ribs at intervals, like the Muricid^e ; the 

 largest species {Triton tritonis) is used by the South Sea 

 Islanders, as a horn or trumpet. A hole is sometimes made 

 in the side of the si)ire to blow through. 



Case III. — The Cowry Shells ( Cypteridce) are remarkable 

 for their varied markings and fine polish, which is produced 

 and preserved by two flaps of the mantle, one on each side, 

 which fold over the back, a line down the centre usually 

 marking where the flaps meet. Cowries are sold as orna- 

 ments ; the Money Cowry fC. moneta) passes current as 

 coin among the negro tribes of Africa and the natives of 

 India. The Orange Cowry {C . aurantium) is worn by the 

 chiefs of Viti, or Fiji, and the Friendly Islands, and is 

 considered the highest order of dignity. C. {Trivia) 

 australis is common on the New South Wales coast. 



The Ovulidce, the most curious of which, the Weaver's 

 Shuttle, {Radius volva), is peculiarly beaked at both ends. 



The Helmet Shells {Cassididce) are used for cameo-carving ; 

 they consist of differently coloured layers, so that the ground 

 colour of the carving is of a diff'erent tint from the subject 

 engraved. 



The Tun Shells {Doliidce) are remarkable for the globose- 

 ness of the shells, which are covered with regular revolving 

 ribs. 

 Case IY. — The Mitras (Mitridce) are great favourites with 

 shell-collectors on account of their beautiful colours and 

 varied sculpture. Mitras are mostly found in tropical or 

 sub-tropical regions. Two of the larger forms are M. 

 episco2)alis and M. papalis. 



