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allied member, the A. Neptunus, Woll. (which may per- 

 haps be in reality but an insular modification of the 

 A. argillosus, Schon., from Teneriffe),has been detected 

 on the rocks of the Salvages, to the north of them ; 

 whilst on the Dezerta Grande, one of the most southern 

 stations of the Madeirau Group, we have a third, which 

 displays far more in common with the Canarian type 

 than it does with that which obtains in Madeira proper ; 

 -which last is gradually, in its turn, merged into the 

 ordinary European form. The genus Pecteropus, Woll., 

 is another instance in point. I possess three or four 

 species from the Grand Canary, Fuertaventura, and 

 Teneriffe ; and I believe it will be found, on inquiry, to 

 attain its maximum in that cluster. Unlike the others, 

 however, which we have just cited, it is powerfully 

 winged ; and we should consequently expect to trace the 

 evidences of its northward progression with comparative 

 perspicuity. Can we therefore do so ? Yes : in Ma- 

 deira proper it has two representatives, and in Porto 

 Santo (to the north of it) one. And so with Xenostron- 

 yylus, Woll. (which is likewise winged), we have two 

 species, at least, in the Canaries ; one in the Madeiras ; 

 and a third, unless I am mistaken, in Sicily. The genus 

 Ditylus is shadowed forth in the Canary Islands by two 

 or three singular representatives of a pallid, testaceous 

 hue ; and, although the group is entirely absent in Ma- 

 deira, a species (the D. fulvus, Woll.) is found on the 

 ' Great Piton ' of the Salvages, so nearly resembling, 

 except in its smaller size, one of those from the Canaries 



