458 TEN YEARS IN SWEDEN. 



Now it is evident that in Ms time as well as at the 

 present day, this 0. pr ester was rarer than the C. berus. 

 The Swedish name was different, and he well described the 

 differences of colour, for in this G. prester which we killed, 

 the black colour was much deeper and duller than in any black 

 viper I had ever before seen (and while living at Trolhattan, 

 south of this, I often used to kill the black viper, but 

 always on wet mosses, never, as in this case, on high 

 ground), and the black line on the back, which Linne gives 

 as a characteristic of the C. berus, was not perceptible in this 

 specimen. 



Now, without placing too much reliance on the number 

 of the squamous plates as a mark of distinction for, like 

 the fin rays of a fish, they may be liable to variation I fancy 

 an accurate and careful examination of the plates of the 

 backs of the heads of these two vipers, might be of some 

 value in determining a distinct species, they are so very dif- 

 ferently shaped and placed. In C. prester the three large 

 plates are much broader than in C. berus, and they are 

 placed .side by side in a straight direction. There are no 

 other plates behind them the scales do not appear so 

 sharp as in C. berus, but broader and rounder, coming 

 close up to them whereas, in 0. berus, the three large 

 middle plates are placed in a slanting direction (at least only 

 the middle one is straight), and there are two more (smaller 

 ones) behind them, in all making five. 



Perhaps, after all, the size and position of these head- 

 plates may be subject to variation, but there is so marked a 

 difference in the appearance of the back of the head of this 

 viper which we killed, and the head of a common black viper, 

 with which we compared it, that if I could only prove, by an 

 examination of some more specimens that this was constant, 

 I should not hesitate to decide that Linne' s 0. prester, was a 

 good and distinct species, and one which, since his time, has 

 been totally overlooked. 



The viper may always be known by the flat head covered 

 with small plates and scales, by the short tail, which occu- 

 pies only one-ninth the length of the body, and a much less 



