CHAP. XIII. ] THE AUSTRALIAN REGION. 407 
Acherusia has 2 species in Brazil, 1 in Australia. These re- 
semblances may probably have arisen from intercommunication 
during the warm southern period, when floating timber would 
occasionally transmit a few larve of this family from island to 
island across the antarctic seas. When the cold period returned, 
they would spread northward, and become more or less modified 
under the new physical conditions and organic competition, to 
which they were subjected. 
We now come to the very important group of Longicorns, in 
which the Australian region as a whole, is very rich, possessing 
360 genera, of which 263 are peculiar to it. Of these about 50 
are confined to the Austro-Malay Islands, 12 to New Zealand, 
and the remainder to Australia proper with Tasmania. Of the 
genera confined to, or highly characteristic of Australia, the 
following are the most important :—Cnemoplites, belonging to 
the Prionide; Phoracantha, to the Cerambycide; Zygocera, 
Hebecerus, Symphyletes, and Rhytidophera, to the Lamiide. 
Confined to the Austro-Malay Islands are Tethionea (Ceramby- 
cide): Zmesisternus, Arrhenotus, Micracantha, and Sybra 
(Lamiide) ; but there are also such Malayan genera as Batocera 
Gnoma, Praonetha, and Sphenuwra, which are very abundant in 
the Austro-Malay sub-region. A species of each of the Austra- 
lian genera, Zygocera, Syllitus, and Pseudocephalus, is said to 
occur in Chili, and one of the tropical American genus, Hamma- 
tocherus, in tropical Australia; an amount of resemblance 
which, as in the case of the Buprestide, may be imputed 
to trans-oceanic migration during the Southern warm period. 
This concludes our illustrations of the distribution of some of 
the more important groups of Australian insects ; and it will be 
admitted that we have not met with any such an amount of 
‘identity with the fauna of Temperate South America, as to 
require us to modify the conclusions we arrived at from a con- 
sideration of the vertebrate groups. 
Land-Shells—The distribution of many of the larger genera 
of land-shells is very erratic, while others are exceedingly re- 
stricted, so that it requires an experienced conchologist to 
investigate the affinities of the several groups, and thus work 
