The geographical distribution of animals, with a study of the relations ...

—chap, xiii.] THE AUSTRALIAN REGION. 407Acherusia has 2 species in Brazil, 1 in Australia. These resemblancesmay probably have arisen from intercommunicationduring the warm southern period, when floating timber wouldoccasionally transmit a few larvae of this family from island toisland across the antarctic seas. When the cold period returned,they would spread northward, and become more or less modifiedunder the new physical conditions and organic competition, towhich they were subjected.We now come to the very important group of Longicorns, inwhich the Australian region as a whole, is very rich, possessing360 genera, of which 263 are peculiar to it. Of these about 50are confined to the Austro-Malay Islands, 12 to New Zealand,and the remainder to Australia proper with Tasmania. Of thegenera confined to, or highly characteristic of Australia, thefollowing are the most important :Cnemoplites,belonging tothe Prionidae ; Phoracantha, to the Cerambycidse ; Zygocera,Hebecerus, Symphyletes, and Rhytidophora, to the Lamiida?.Confined to the Austro-Malay Islands are Tethionea (Cerambycidse): 1 mesisternus, Arrhenotus, Micracantha, and Sybra(Lamiidae) ;but there are also such Malayan genera as BatoceraGnoma, Praonetha, and Sphenura, which are very abundant inthe Austro-Malay sub-region. A species of each of the Australiangenera, Zygocera, Syllitus, and Pseudocephalus, is said tooccur in Chili, and one of the tropical American genus, Hammatochccrus,in tropical Australia ; an amount of resemblancewhich, as in the case of the Buprestidae, may be imputedto trans-oceanic migration during the Southern warm period.This concludes our illustrations of the distribution of some ofthe more important groups of Australian insects ; and it will beadmitted that we have not met with any such an amount ofidentity with the fauna of Temperate South America, as torequire us to modify the conclusions we arrived at from a considerationof the vertebrategroups.Land-Shells.—The distribution of many of the larger generaof land-shells is very erratic, while others are exceedingly restricted,so that it requires an experienced conchologist toinvestigate the affinities of the several groups, and thus work