22 



(PfeiflFer), Sweden (Nilson), France and Belgium 

 (Forbes). 



As a fossil it is found in the tertiaries, contempora- 

 neously with the drift when the British Isles were 

 under the sea (Forbes). 



The variety of some authors, called Unio ovalis (or 

 the Oval Union), is thick, and assumes a yellowish 

 green colour. Hereabouts it is found associated with 

 Unio tumidus, from which it scarcely difl'ers. 



Unio Pictorum (The Painter's Union). Linnccus. 

 Figure 10. 



10 



The form of Un»o pictorum varies much more than 

 that of Unio tumidus, being chiefly from an elongated 

 oval-oblong to a somewhat produced ova), and at times 

 being very much produced. The umbones are com- 

 pressed. The epidermis, which is brilliant, is of an 

 olive-yellow, changing posteriorly into an almost green 

 colour. The two sides of the shell (by which we mean 

 the upper and lower edges) are nearly horizontal. 

 There is an elongated projecting ligament. The 

 primary teeth are coarsely crenated and flattened; the 

 hinder teeth scarcely to be recognized. In recording a 

 fine specimen, Professor Forbes gives the following di- 

 mensions :— Length, 3 inches; breadth, nearly 2| 

 inches. The largest specimen taken in this neighbour- 



