216 
ZOOLOGICAL LITEllATUllE. 
He adds that Helix {Cochlicella) acuta (MUll.) has been found 
near Nykjobing on the north-western coast of Jutland, with 
Cy do stoma eleganSj and is probably introduced. He says that 
the peasants are in the habit of fumigating the stables with 
ginever-shrubs, which they buy from apothecaries. One of the 
latter, a conchologist, has found among his stock of that plant 
some Saxon shells not yet observed in Denmark, as Buliminus 
detritus (Mull.), Helix ericetor urn (Miill.), Papa avena (Drap.). 
This may be one Avay of introducing foreign shells into a country. 
Martens, E. v. Eine eingewanderte Muschel. Zoolog. Gart. 
Frankf. 1865, pp. 50-59, 89-97. [An instance of the mi- 
gration of a Bivalve. See Zool. Becord, i. p. 191] . 
Dreissena polymorpha was not known in the northern and 
western halves of Europe some forty years ago. The numerous 
treatises on the mollusk-faunas of these countries published at 
the close of the past and in the first two decads of the present 
century do not mention it. All at once it was observed for the 
first time in tributaries of the Baltic, the Niemen and Weichsel, 
in the year 1825, in tributaries of the Elbe in 1828, in the 
terminal branches of the Bhine in 1826, and in England in 
1824. Several direct observations, and the comparison of the 
localities and times in which it has been observed for the first 
time in the several countries, establish the fact that it has been in- 
troduced into all those parts of Europe, along artificial, navigable 
canals, by means of ships or timber, and even across the channel 
to England. The belief that it was observed already towards 
the close of the past century in south-western Germany is 
founded on a very superficial description of a shell by Sander, 
and contradicted by the negative evidence given by Prof. Alex. 
Braun for the years 1824-1816 and by Hr. Gysser for the pre- 
sent time, both agreeing in never having met with Dreissena in 
that part of Germany. As regards the rivers near to the Black 
and Caspian Seas, no reliable or sufficiently complete record of 
their faunas has been preserved from the commencement of this 
century ; and there is consequently no reason to think that a 
recent migration has taken place into the Danube and the rivers 
of southern Bussia. At present it inhabits nearly all the tri- 
butaries of the Baltic, the Elbe upwards to Halle, the Bhine 
upwards to Huningue, the rivers of northern France, including 
the Loire, the British Islands, Hungary, a part of European 
Turkey, and almost the whole of Bussia. It is very desirable 
that the attention of conchologists should be directed to the 
further advance of this shell, and that accurate statements should 
be made as regards the time at which it first appears in the lists 
of local faunas, not having been mentioned by previous accurate 
observers. 
This species is really a freshwater shell ; it does not live in the 
