British Freshioater Entomostraca. 359 



with Dr. Scott's description and figures of C. hirticomia 

 leaves no doubt that both WL-re dealing with the same 

 species. As SclimeiFs name lias priority, it is unfortunate 

 that the specific name of liirt'icornis must give way to that 

 of rapiens. Prof. Sars is undoubtedly right in including 

 the species in the genus Mesochra. 



Mesuchra rapiens is fairly common in the Norfolk Broads, 

 where the salinity is high {e. g., HicUliiig and Horsey), and 

 I have also found it at Flordou Common, near Norwich. 

 The water there is perfectly ^' fresh," but is highly calcareous, 

 and my specimens were found in greyish calcareous mud, 

 covered only by a mere film of water. It occurs also in 

 Oulton Broai!, in Suffolk, since a slide iu Pr. Brady's 

 collection, labelled " Cantliocamptus palustris, Oulton Broad," 

 contains, besides several C. palustris, also two specimens of 

 Me.<iochra rapiens and one of Tackidius Uttorulis, L-*oppe. 

 This slide was probably made before the year 1880, 



M. rapiens has been found by Dr. Scott in various parts 

 of Scotland (Outer Hel)rides, Loch Tarbert, Forth District, 

 Loch Lomond, and R. Ythan, Aberdeenshire), often in 

 brackish water and always not far from the sea. Iu the 

 Baltic it has been recorded from Colberg by Schuieil in water 

 of a salinity of "5 °/^, and by Lilljeborg from the Baltic coast 

 and from the Ekoln branch of Lake Malaren in fresh water. 

 I'rof. Lilljeborg suggests that it may be regarded as a relict 

 in Ijake Malaren of a former extension of the Baltic. The 

 Ekoln is known to contain other Crustacea which are supposed 

 to be relicts of such former extensions*. In Norway the 

 species has only been taken in a brackish pool iu the South. 



6. Tuchidias brevicornis, Lillj., in fresh water. 



Mr. Sconrfield t has drawn attention to the small pools 

 of water which collect at the roots and in holes in trees as 

 the habitat of Entomostraca, and has described a new 

 species, Muraria arboricolu, which inhabits such pools iu 

 E])ping Forest. In Kpping Forest the j)ollarding of the 

 oaks has |)rovided innumerable water-holes, but I found, 

 during a visit to the New Forest in August 1919, that the 

 only collections of water there were in beech-trees, either at 

 the roots or in tiie hollow in the fork between two main 

 branches, though there were other holes which had at one 

 time contained water, but were then dry. Moraria arboricolu 

 proved to be common, occurring in the majority of the pools, 



* Ekman. Z(if>l. Stticl. tillap-n. T. TuUberp, 1907. 

 t Jourii. (^lekttt Mic. Club, (!.') xii. l!Ho, p. 431. 



