352 Mr. R. Gurney on certain 
Lyndhurst-Ringwood road. There are several small ponds 
along this road within a short distance of each other, but 
this one alone contained the Chirocephalus. All the ponds 
have a gravel bottom covered with grassy weed, and the 
only respect in which the pond in question differed from the 
others was in the presence of a thick growth of Polygonum 
hydropiper. None contained Cladocera of any kind, but, 
whereas the other ponds examined produced only Diaptomus 
castor and Cypris virens, the Chirocephalus was accompanied 
by Cyclops agilis and C. vicinus, Diaptomus vulgaris, and 
Cyprinotus incongruens. 
The first record of the occurrence of Chirocephalus dia- 
phanus in Britain is that of King, who found it near 
Norwich in 1762. Baird, in 1850, was able to give several 
records of its occurrence, and in 1862 it was found by 
Mr. A. Brady at Tillmire, near York. From that date till 
1891 it was apparently not met with, but since then it has 
been seen in about twenty places, nearly all in the South of 
England. It is possible that the absence of records of the 
occurrence of Chirocephalus (with the exception of that of 
1862) from 1850 till 1891 may be due to lack of search for 
it, but it seems more probable that it actually disappeared 
in the same way as Apus cancriformis became extinct. The 
latter appeared again in 1907, but did not establish itself ; 
whereas it seems that Chirocephalus diaphanus has not only 
re-established itself, but is becoming comparatively common. 
Its most northern locality in England corresponds almost 
exactly with its northern limit (50° N. lat.) in Europe, and 
its range extends South to the maritime regions of Algeria 
and Tunisia. It does not, so far as I know, occur in the 
Hauts Plateaux of Algeria or at Biskra. Daday quotes my 
authority for its occurrence at Biskra, but this is an error 
on his part, as the only species found there by me was 
Branchipus pisciformis, Schaeffer. 
Chirocephalus diaphanus ranges in size from 37 mm. down 
to 12 mm., and Simon® states that there are two distinct 
races—a large and a small—which do not intermingle. My 
specimens from Bratley Heath, though fully mature, mea- 
sure only about 16 mm., but much larger specimens occur 
in this country. I have a female, taken in Cornwall, of 
30 mm., and Mr. Scourfield informs me that he has one 
from Christchurch nearly 34 mm. long, though the largest 
specimens from Claygate do not exceed 19 mm. _ Both 
races are recorded by Simon from North Africa, and I have 
* Ann. Soc. Entom. France, ser. 6, vi. 1886, p. 397. 
