1902-1903-] Distribution of the Smaller Crustacea, 29 



to our shores by a more than usual southward trend of cold 

 water from the North Atlantic. The following examples will 

 illustrate this migration of sub -arctic and arctic forms. 

 Thalestris krohnii (Kroyer) (=Thalestris serrulatus of Brady's 

 Monograph) is a free-swimming arctic copepod, of a brick-red 

 colour when living. This copepod has been recorded from 

 various parts of the Arctic Sea, off the coasts of Finmark, and 

 between Novaya Zemlia and Spitzbergen and elsewhere. 

 But though a decidedly northern species, it sometimes makes 

 its way far to the southward. Dr Brady, in his ' Monograph 

 of the British Copepoda,' records its occurrence at the Scilly 

 Isles (1880); I. C. Thompson obtained it near Puffin Island 

 (Irish Sea) in 1889; and in 1890 I reported its occurrence 

 in the Firth of Forth and in Dornoch Firth. My son has 

 also obtained it in a surface gathering from the Gulf of St 

 Lawrence. In all these instances, however, so far as known 

 to me, it occurred very sparingly. 



The next species I would refer to is the amphipod 

 Uuthemisto compressa (Goes). In 1892 an immense shoal of 

 Mithcmisto cowpressa was observed off the Yorkshire coast. 

 The sea was described as literally alive with them, and great 

 numbers were afterwards washed ashore by sea-winds, and 

 afforded a feast for starlings and other frequenters of the 

 tidal line (see T. H. Nelson in tlie ' Naturalist ' for May 

 1892). Some of the specimens made their way into the 

 Firth of Forth, and were captured in the tow-nets of the 

 fishery steamer which was at that time in the Forth estuary, 

 being mentioned among the " records " for that year. This 

 species is not uncommon in the Arctic seas. It is interesting 

 to notice that in 1891 and 1892 there was also a considerable 

 increase in the numbers of Paratliemisto ohlivia (Kroyer) taken 

 by our tow-nets. The greatest increase inside the estuary 

 occurred in 1891, while at the mouth of the estuary the 

 greatest increase observed was in 1892. The cause of this 

 remarkable southward migration of Eutheviisto compressa along 

 our east coast might be due to an unusual southerly move- 

 ment of cold water from the North Atlantic. No similar 

 migration has been observed in recent years. 



In 1893 I reported the occurrence of the sub -arctic 

 amphipod Anonyx nugax (Phipps) in the vicinity of May 



