1912. j S. Kemp : Notes on Decapoda. 119 



great central sea now represented by the N. Atlantic and the 

 Mediterranean, there existed a ' Sino-Australian ' continent. This 

 involved Eastern Asia, the Indo-Mala3"sian Archipelago and 

 Australia, extending southwards to the Antarctic regions and 

 from it a tongue of land reached out to New Zealand by way of 

 New Guinea and Norfolk Island. During Upper Cretaceous times 

 the ' Sino-Australian ' contin ;>nt was divided b}' a neck of water 

 extending across the region now occupied by vSumatra and Celebes 

 and the land extension from Madagascar to vS. India reached north 

 to the northern or Asiatic part of that continent. In I^ower and 

 U])per Tertiar}- times New Zealand was completely isolated as it 

 remains ^t the present day ; in the former period India was merely 

 an island, an eastern sea-connection between the ' ^Mediterranean ' 

 and Indo-Paciiic extending across Assam and Burma, while in the 

 latter it approaches the shape which it at present bears. 



On these theories the explanation of the discontinuous distri- 

 bution of X. C'urvirostris is possible, though it can hardly be said to 

 be very convincing. We must assume that Xiphocaridina curviros- 

 tris evolved from some unknown marine or freshwater ancestor in 

 earl}" Cretaceous or pre-Cretaceous times and remained unchanged 

 until the present da}-. In the Lower Cretaceous period it would 

 have opportunities of spreading to New Zealand on the one hand 

 and to lyower Burma on the other. Subsequently, while becoming 

 isolated in New Zealand it must have persisted in Burma or in the 

 country existing to the west of it until Assam reappeared during 

 the Upper Tertiary period. 



The existence of Xiphocaridina compyessa both in China and 

 Japan and in Australia seems to show that this species also^ 

 according to Ortmann's theories, must have remained with- 

 out sensible modification for almost as long a period. Every 

 zoologist will readily call to mind other instances tending to a 

 similar conclusion. 



Although no exactly parallel case of geographical distril)ution 

 seems to be known among freshwater Crustacea, the ]\Iegascolecid 

 Oligochaeta of the sub-family Octochaetiuae afford an instance of 

 a closely similar nature. According to ^lichaelsen (1909) this sub- 

 family is found onh^ in India and New Zealand ' and although no 

 species appear to be common to the two, two genera, Octochactus 

 and Hoplochaetclla, occur in both localities. 



Michaelsen holds that the only possible interpretation of these 

 facts is that at one period a direct land connection existed be- 

 tween India and New Zealand. He remarks (p. 203) : '' T need not 

 explain to any zoo-geographer that the discontinuation of these 

 two regions of distribution in the Octochaetinae is quite a com- 

 mon matter in geographical distribution, the two regions, New 

 Zealand and India, perhaps together with a third region, Mada- 

 gascar, the home of Howascolex, representing the peripheral parts 



1 Michaelsen mentions that another genus, Howascolex, known only from 

 Madagascar, might perhaps also be regarded as a member of this sub-family. 



