49 



and are clearly indigenous species ; and many other 

 similar instances, both at home and abroad, might be 

 cited on this point, as well as with respect to the sudden 

 and unaccountable appearance and disappearance of cer- 

 tain species in particular spots. With regard to the 

 period at which the Dreissena first made its appearance 

 or was noticed on the Continent, M. Moerch has lately 

 investigated its geographical history and has ascertained 

 that it was common in the interior of Germany before 

 1780, and that it then inhabited streams which flowed 

 into the Rhine. In a work by H. Sander of Carlsruhe, 

 published in that year, and entitled " Vaterlandische 

 Bemerkungen fiir alle Theile der Naturgeschichte," he 

 described in unscientific, but intelligible, terms a fresh- 

 water Mussel which was not uncommon in that district, 

 and to which he gave the name of Pinna fluviatilis. This 

 description clearly applies to our Dreissena. In draining 

 the Haarlem See, the Dreissena was found in abundance ; 

 and it appears that no communication ever existed be- 

 tween that great lake and any port or harbour. It has 

 also been found in an inland lake near Copenhagen. It 

 was at one period thought (and even by the unimagi- 

 native Liun6) that the Teredo^ or ship-worm, had been 

 imported into Europe from India; but that idea has 

 been quite dispelled, as much for the reason that some 

 species of Teredo which are found in Europe also occur 

 there in tertiary formations, as because they are different 

 from oriental or tropical kinds. The first of these reasons 

 may again, and with the like success, be urged in favour 

 of the Dreissena being a native of the North of France ; 

 for, in a recent article by M. Charles D'Orbigny, pub- 

 lished in the ' Bulletin de la Societe Ge*ologique de 

 France ' (2 e se"r. t. xvii. p. 66), and entitled " Sur le 

 diluvium a coquilles lacustres de Joinville," Dreissena 



