34 CRUSTACEA—BRANCHIOPODA CHAP. 
the sea; Apus cancriformis has, however, been found in Armenia 
at 10,000 feet above sea-level. 
Wells and underground waters do not generally contain 
Phyllopods; but a species of Branchipus and one of Limnetis, 
both blind, have been described from the caves of Carniola. 
One of the many puzzles presented by these creatures is the 
erratic way 1n which they are scattered through the regions they 
inhabit; a single small pond, a few yards or less in diameter, 
may be the only place within many miles in which a given species 
ean be found; in this pond it may, however, appear regularly 
season after season for some time, and then suddenly vanish. 
Geographically, the Phyllopoda are cosmopolitan, represen- 
tatives of every family and of some genera (e.g. Streptocephalus, 
Lepidurus, Estheria) being found in every one of the great zoo- 
logical regions, though a few aberrant genera are of limited range, 
thus Polyartemia is known only from the northern Palaearctic 
and Nearctic regions, Thamnocephalus only from the Central 
United States. The genus Artemia is not at present known in 
Australia." The only recorded British species are Chirocephalus 
diaphanus, Artemia salina, and Apus cancriformis, but other 
continental islands, for example the West Indian group, are 
better supphed. The distribution of the species is very im- 
perfectly known, but on the whole every main zoological region 
seems to have itS own peculiar species, which do not pass beyond 
its boundaries. Branchinecta paludosa and Lepidurus glacialis are 
circumpolar, both occurring in Norway, in Lapland, in Greenland, 
and in Arctic North America; but with these exceptions the 
Palaearctic and Nearctic species seem to be distinct. The Euro- 
pean species Apus cancriformis occurs in Algiers, but the relations 
between the species of Northern Africa as a whole and those of — 
Southern Europe on the one hand, or of Central and Southern 
Africa on the other, have yet to be worked out. | 
The soft-bodied Branchipodidae are not known in the fossil 
condition ;° an Apus, closely related to the modern -A. cancriformis, 
has been found in the Trias, but the most numerous remains have 
been left, as might be expected, by the hard-shelled Limnadiidae ; 
1 Sayce has since described it, Proc. Roy. Soc. Victoria, xv., 1903, p. 229. 
2 A. cancriformis had been supposed to have disappeared from the British fauna 
for many years, but it was found in Scotland in 1907. See R. Gurney, Nature, 
Ixxvi., 1907, p. 589. 
3 Branchipodides has been deseribed by H. Woodward, from Tertiary strata. 
