322 Prof. 0. Heer on the House Ant of Madeira. 



these might even be considered as a single natural genus. 

 But to such as study the INlollusca of a larger and more pro- 

 lific district, and especially the species now contained in col- 

 lections brought from various climes, such a union of genera 

 seems to me most undesirable, particularly as it prevents that 

 accuracy of observation and discrimination which it is the great 

 advantage of natural history as a branch of education to establish 

 and teach. 



" From the study of the animals, shells and opercula of these 

 Lamarckian genera, I have been induced to form the group into 

 the following families, viz. Rotelladce, Turhinidce, Liotiadce, Tro- 

 chida, Stomatellada, Scissurellada, Haliotidce and Fissurelladce. 

 I believe that Scissurella is very distinct from Ti'ochus, and inter- 

 mediate between it and the Haliotida, but more nearly related to 

 the latter than the former ; and this view of its position has been 

 strengthened by Mr. Barrett^s description of the animal, as well 

 as by what you say as to the operculum and structure of the 

 shell. 



" Though the family of Scissurellada only contains one, or as 

 you have very properly proposed, two genera, yet they appear 

 to be all that remain of a large number of fossil genera, con- 

 taining together more than 300 well described and figured 

 species. 



" I never believed that Scissurella had any relation with 

 lanthina, and the figure and description of the animal distinctly 

 prove that it has not any. 



" Adeorbis, on the other hand, is clearly a genus belonging to 

 the same great group above mentioned, and is referable, by the 

 exquisite structure of its operculum, to the family Liotiad(S, 

 characterized by its horny many-whorled operculum being orna- 

 mented with concentric spiral lines of a calcareous pearly sub- 

 stance. 



" Ever yours sincerely, 



"J. Gwyn Jeffreys, Esq." "J. E. Gray." 



XXVII.— 0« the House Ant of Madeira. By Prof. 0. Heer, of 

 Zurich. Translated from the original by R. T. Lowe, M.A. 



[Concluded from p. 224.] 



II. Description of the House Ant. 



(EcoPHTHORA, Heer. 



Mandibles very strong, in the females and soldiers with a 

 sharp cutting edge, in the labourers toothed like a saw. Palpi 

 of the tongue and maxillse vei-y short and two-jointed; the 



