352 Mr. R. Gurncy on certain 



Lyiullnirst-Ringwood road. There are several small ponds 

 aloufij this road within a sliort distance of eaoli other, but 

 this one alone contained the Cliiroccfhalus. All the ])onds 

 have a gravel bottom covered witli j^rassy weed, and the 

 only respect in which the pond in question differed from tlie 

 others was in the presence of a thick growth of Pohjt/ouum 

 hijdropiper. None contained Cladocera of any kind, but, 

 whereas the other ponds examined produced onl}' Diajifonnts 

 castor and Cijpris virens, the Chirocephalm was accompanied 

 by Cyclops nyilis and C. vicinus, Diuptomus vulgaris, and 

 Cyprinoius mcongruens. 



The first record of the occurrence of Chirocephahis dia- 

 ])hanus in Britain is that of King, who found it near 

 Norwich in 176.2. Baird, in 1850, was able to give several 

 records of its occurrence, and in 18G2 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 

 occuricnce of Chirocephalus (with the exception of that of 

 18H2) 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 aj)peared again in 1907, b\it did not establish itself ; 

 whereas it seems tliat Chirocejihalus diaphanits 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, nnd 

 its range extends South to the maritime regions of Algeria 

 and Tunisia. It does not, so far as I know, occur in the 

 Hants Platea\ix of Algeria or at Biskra. Daday quotes my 

 authority for its occurrence at Biskra, but this is an error 

 on iiis j)art, as the only species found there by me was 

 Brancliipus pisciformis, Schaeffer. 



Chirocephahis diaphanus ranges in size from 37 mm. down 

 to 12 mm., and Simon* states that there are two distinet 

 races — a large and a small — whicli do not intermingle. j\Iy 

 specimens from Bratley Heath, though fully mature, mea- 

 sure only about IG mm., but much larger specimens occur 

 in this country. I have a female, taken in Cornwall, of 

 30 mm., and Mr. Scourfield informs mc that he has one 

 from Christchurch nearly 34 mm. lung, though the largest 

 S|)ccimens from Claygate do not exceed 19 mm. Both 

 races are recorded by Simon from North Africa, and I have 



* Auu. Soc. I'Jitoin. i'lRuct'. scr. r>, vi. Is8(), j). 307. 



