88 SCALARIIDiE. 



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 Bulla 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 pui^pose of examination " fed eagerly upon 

 fresh beef J especially if somewhat macerated. '^ The 

 animal of every species of Scalaria emits a purple dye, 

 like Planorbis coiiieus, layithina, 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. H. 3rd ser. xvi. p. 397. 



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



