658 MRS. E. W. SEXTON ON 



uropofls, and the telson ; in some cases these long hairs appear to 

 replace the spines of the hrackish-water form, e.g. those inset on 

 the inferior margins of the 2ncl and 3rd pleon epimera and the 

 posterior margins of the 4th and 5th perseopods. 



The finest brackish-water specimens I have seen come from 

 the Konigsberg Collection, taken at Ranschen and Zoppot, the 

 lai'gest freshwater ones from the Hamburg " Wasserleitung." 

 These are larger than any of the others examined by me, pi'obably 

 owing to the more protected life they lead in the underground 

 pipes, and the rich and constant supply of food. 



The collections I have examined are as follows, with the names 

 of those to whom I am greatly indebted for the opportunity of so 

 doing : — 



1. lumigsherg Museum: Dr. Liihe. Four tubes containing 

 Zaddach's specimens and others from Danzig Bucht, Zoppot, 

 Koliebk, Redlan, and Rauschen, in all about 125. Most of the 

 specimens are of the typical brackish-water form, but in one 

 sample from Danzig in which a specimen of the freshwater 

 G. jndex was also found, many of the animals were "intermediate " 

 forms, more solidly built and with the long fine hairs developed 

 in great numbers. 



2. Finsches Haff: Dr. Vanhoffen. Two tubes labelled " Gam- 

 marus locusta L. Frisches Half bei Pillau Ostpreussen. 20. ix. 1911 . 

 YanhofFen. 5." One tube contained 16 specimens, 2-5*5 mm. in 

 length. It is interesting to note a few young Leptocheirus 

 pilosus with the young G. zaddachi ; these two species, with 



Gorojjhhmn volutator and G. lacustre, seem to flourish equally well 

 in fresh or brackish water and are frequently recorded together. 

 There were 8 specimens of G. zaddachi in the second tube, 3'5- 

 10 mm. long, all of the brackish-water form ; the largest, however, 

 approaching the freshwater form, strongly built and opaque. 



3. Mouth of the Oder : Dr. YanhoflTen. One tube, " Gammarus 

 locusta L. Dievenow Odermundung Pommern 1889. Hilgen- 

 dorf . 5." 26 specimens, 1 young male G. locusta and 25 G. zad- 

 dachi exactly like those described from Pillau. 



4. Mouth of the Elbe, from Schulau to Gauert, together with a 

 collection from the Hainhurg Wasserleittivg ; Dr. Steinhaus. This 

 is a most interesting series taken at regular stations in the Elbe 

 (see Volk, with map of the district), containing in all about 500 

 specimens. Commencing with the stations nearest the mouth of 

 the river, where the water has nearly the full salinity of the 

 North Sea, the details are as follows : — 



"Slider- Elbe siidl. Blankanese. Grund. ll.vi.OO." 11 speci- 

 mens 4-10 mm. 



" Hafen siidl. Nienstedten. Grund. 2.vi.00." 35 specimens 

 1"5-10 mm. 



" Hafen siidl. Nienstedten. ll.vi.OO." 3 specimens, largest a 

 female 11 mm. 



" Linkes Elb-Ufer siidl. Nienstedten. 2.ix.00." 3 specimens, 

 largest a female 8 mm. 



