66 



islands, is but a local state of the A. depressum, Grav., 

 of Central Europe. The Bembidium tabellatum and 

 Schmidtii, Woll., may be in reality but geographical 

 modifications of the B. tibiale and callosum of higher 

 latitudes ; and the Malthodes Kiesenwetteri, Woll., of 

 the common European M. brevicollis. Calcareous deposits 

 would appear, ever and anon, to have considerable effi- 

 cacy in regulating the outward aspect of such species as 

 are able to adapt themselves to different geological 

 districts ; and when in juxtaposition with the shore, 

 their effects are often very conspicuous. The Dromius 

 arenicola, Woll., is the Portosantan representative of 

 the D. obscuroyuttatus, Dufts. ; and distinct as it is in 

 colouring from that insect (as evinced both in Madeira 

 proper and throughout Europe), I believe it to be in 

 reality but a local condition of it, occasioned by a resi- 

 dence through a long series of ages on a calcareous soil. 

 For the same reason perhaps (though assisted, in all 

 probability, by the qualifying power of isolation), the 

 Hadrus illotus, Woll., may be specifically identical with 

 the Madeiran H. cinerascens. In like manner, the Bem- 

 bidium Atlanticum, Woll., which in Madeira proper is 

 frequently so dark that its elytral patches are sub- 

 obsolete, and which is but seldom brightly arrayed in 

 that island, assumes in Porto Santo (which is not only 

 more calcareous than the central mass ; but is strongly 

 impregnated, as its streams and rills everywhere testify, 

 with muriate of soda) a permanently paler hue, being 

 at times almost testaceous. Some districts seem to be 



