418 
HORN EXPEDITION—ZOOLOGY. APPENDIX. 
worm fauna at the time, which may perhaps go as far back as the Lower 
Cretaceous age, when such animals could pass across into the central area of 
the continent. At the present time the now characteristic genera—Megasco- 
licles and Cryptodrilus —have the centre of their distrilnition in the south-eastern 
part of the continent, and are probably to be regarded as being indigenous to this 
portion, from which they have spread in vai'ious directions around the coastal area. 
Other genera, the systematic position of which is not at present at all clear, but 
which have as yet been described by Mr. Fletcher and myself under the general 
name of Periclueta,* and which form in point of number the greater part of the 
present Australian earthworm fauna, are partly to be regarded as developed 
within the limits of the continent, and partly as probable immigrants from the 
oriental region. It is certainly curious, supposing them to have existed side by 
side with Acanthodrilus in Pre-Tertiary or early Tertiary times, that none seem to 
have made their way across into the centre of the continent. 
Whilst the evidence is admittedly slender, still it points in the direction of 
Acanthodrilus being an ancient genus, and as forming the dominant one in the 
north-eastern part of the continent at the time when favourable conditions allowed 
of the migration of such soft-bodied and moisture-loving creatures as earthworms. 
It is interesting also in this connection to note amongst the Molluscs the 
presence of Microphyura hemiclansa, belonging to a genus which Mr. Hedley 
regards “from its distribution and anatomy to be of high antiquity and of Antarctic 
origin,” and as perhaps one of the most primitive of Australian snails. 
Like Acanthodrilus, Microphyura is found on the continent only in Queens¬ 
land, but is also recorded from New Caledonia and the Loyalty Islands. 
Probably Microphyura and Acanthodrilus entered Australia at the same time, 
and the relics of both genei’a left stranded in the centre ai’e to be regarded as 
representatives of genera which once had a wide distribution over the north and 
north-eastern part of the continent. 
The following is a description of the species :— 
Acanthodpilus eremius, sp. n. Length of spirit specimen 85 mm., 
breadth about 2 mm. Number of segments about 130. 
Prostomium not completely dovetailed into the peristomium (about one-half). 
* These forms have been placed in various genera by Mr. Beddard in liis recent in\ alualjle monograph on the 
Oligochseta, but as a re-arrangement of these will be ultimately necessary, I have here spoken of them as 
Pericha3ta, under which name they were described. 
