34 Dr. B. Lysholm and O. Nordgaard. 
terranean, and must be ascribed to an inflow of cold water into 
the northern Atlantic. 
To explain the peculiarity in the distribution of H. acuti- 
jrons it is necessary to assume both a Mediterranean and a polar 
centre of distribution. The natural consequence of such a sup- 
position is, that the said species in the Mediterranean must be 
an arctic relict. To this we find analogies in the benthonic 
fauna. Among the Bryozoa there is a species, Retepora cellulosa 
LIN; Which is recorded from the Mediterranean and from arctic 
waters, but has not hitherto been found at the British isles. R. 
cellulosa is also noted from tertiary strata of Italy; the species 
has passed into the arctic fauna with characters quite unaltered, 
and this is possibly also the case with H. acutifrons. Palæonto- 
logical proofs in support of this view, however, can hardly be 
advanced. | 
Mormonilla minor was described by ciessrecnt (1892) from 
the Pacific, 3° S. Lat. The Nansen polar expedition brought 
home specimens oi a Mormonilla, of which G.0.SARS') says: 
>It seems to agree best with the species named by GIESBRECHT 
M. minor; but the agreement is not quite perfect, and, as the 
places where these 2 forms were found are so widely remote, 
I prefer to describe the polar form provisionally as a new spe- 
cies, leaving the ultimate decision regarding the identity or non- 
identity of the two forms for future investigations<. sars named 
the polar form Mormonilla polaris. In 1895, worrenpen» had 
described another species, M. atlantica, from a station south-west 
of Ireland. In 1908 Farran» also recorded M. minor from off 
the coast of Ireland, and this author is of opinion, that polaris 
and atlantica are identical with minor. We cannot decide the 
question, but suppose it to be not improbable that FARRAN is 
right. Thus M. minor may be regarded as an arctic species 
transported to the North Atlantic by arctic currents. Another 
species described by ciessrecnt, M. phasma, is certainly a southern 
form, which according to FARRAN coincides in the North At- 
lantic with M. minor. According to &GIESBRECHT this is also 
the case in the Pacific. 
MENN. RE. 04120. 
NI PS på 16. 
5) Ry CoA. p88: 
