88 SCALARIIDjE. 



In this family and genus occurs for the first time a 

 retractile proboscis or " haustellum/' instead of a con- 

 tractile snout or " rostrum/' Morch* suggests that 

 there may be no greater difference between these two 

 organs than between a long and a short siphon. The ar- 

 mature of the tongue is very simple, and consists of a 

 single row of uniform teeth on each side without any in 

 the middle ; it agrees nearly with that of Homalogyra 

 and the Sulla tribe. Without presuming to disparage 

 the labours of those conchologists who may be termed 

 odontological systematists, I think an undue importance 

 has been given to this character as a basis of classifica- 

 tion for the Gastropoda. The alimentary and masti- 

 cating organs of all animals depend on the nature of 

 their food ; and every division of the Gastropoda con- 

 tains some kinds which are phytophagous and others 

 which are sarcophagous or zoophagous. Scalaria be- 

 longs to the latter class. According to Dr. Gould, a 

 specimen of S. Grcenlandica which Mr. Couthouy kept 

 alive for the purpose of examination "fed eagerly upon 

 fresh beef, especially if somewhat macerated." The 

 animal of every species of Scalaria emits a purple dye, 

 like Planorbis corneus, lanthina, and Aplysia. The use 

 of this secretion is not sufficiently known f. Montagu 

 made some curious experiments with the dye of S. com- 

 munis, showing that the colour is changed by the appli- 

 cation of mineral acids, and that it is not affected by 

 cream of tartar, nor materially by either volatile or fixed 

 alkali; that it is not diminished by putrefaction, nor 

 fixable by any then known astringent ; it resisted for 

 some months the action of the air and sun ; but being 

 exposed for a whole summer to the solar rays in a south 



* Ann. & Mag. N. II. 3rd ser. xvi. p. 397. 



t See vol. i. (Introduction) pp. xxxv and xxxvi. 



