ALBURNUS LUCIDUS. 



235 



remains consists of oblong particles of rectangular form four times as long as 

 wide. Some authors determine this substance as phosphate of lime, others as 

 phosphate of magnesia. The iridescence has been attributed to the presence 

 of guanin. / 



Mons. Selys-Longchamps described a variety of the Bleak in Belgium 

 in which the rays of the anal fin are shorter than in the German types ; but 

 intermediate forms are found. Heckel and Kner mention a variety known as 

 Alburnus lacustris, in which the height of the body is conspicuously greater, 

 especially in the young fish. It acquires its varietal name from inhabiting 

 the Nieusiedler See and Flatten See. 



This variety closely resembles a fish from the Danube, which the same authors 

 name Alburnus breviceps,\\\i\Q\i shows no important differences (Fig. 



Fig. 132. ALKURNUS LUCIDUS, VAH. BKEVICEPS (HECKEL AND KNER). 



In it the silver tint is less bright. The forehead is broader, so that the eyes 

 are more distant from each other ; and the head is a little shorter. The 

 common length is about five inches. The Alburnus fabrai of Blanchard, 

 found up the Rhone, is a similar fish, with a well-rounded back. 



In the Lakes of Geneva and Bourget a Bleak occurs, which Blanchard 

 names Alburnus mirandella. Its body is more elongated than in the Common 

 Bleak. The scales are stronger, and there are fifty-seven to fifty-eight in the 

 lateral line. The back is nearly horizontal. The lower jaw is a little longer 

 than the upper. The colour recalls that of the Sardine, by which name it is 

 known in Savoy. 



These varieties are instructive, as showing the capacity of the species to 

 vary in different details of organisation. 



