THE FRESH-WATER FISHES OF EUROPE. 



His hand is constantly at the mill-spout to ascertain the quality of the 

 meal produced, so that his thumb becomes the gauge of value of the pro- 

 duce, and this has led to the adage " worth a miller's thumb," and the 

 proverb "an honest miller hath a golden thumb." It is remarkable how 

 the thumb of the miller comes by incessant use to resemble the head of 

 the fish which is usually found in his mill-stream. In Sweden its popular 

 name is Simpa. 



There are two varieties of this species, which were regarded as of specific 

 rank by Heckel and Kner, but their true nature was indicated by Dr. Giinther. 

 One of these is the variety microstomus, the other the 

 variety ferrugineus. There is considerable difference in 

 the form of the head in these varieties, as may be seen 

 in the profile and in the front view of the face (Figs. 

 20, 21, 22, 23). Coitus microstomus has the head smaller 

 in front, as seen from above ; it is less blunt, has a smaller 

 mouth ; while the eyes are larger, with a greater diameter than the distance 

 between them, and the spine of the pre-operculum is more developed, and the 



Fig. 21. HEAD OF COT- 

 TUS MICUOSTOMUS, 

 SEEN FROM THE 

 FRONT. 



Fig. 22. COTTUS GOHIO, VARIETY FERRUGINEUS (HECKEL AND KNER). 



bands of teeth on the pre-maxillary and vomer are broader. The caudal fin is 

 less rounded than in Cottus gobio, its six middle rays subdivide twice, while the 

 rays above and below are simply forked, and are succeeded at the outer 

 parts of the fin by three or four undivided rays. The lateral canal opens 

 by thirty-four or thirty-five pores, a larger number than is found in Cottus 

 gobio. The skin is smooth, but has a rough texture on the upper part of 

 the head arising from a multitude of small ossifications like the minute 

 dermal bones which are embedded in the skin above and below the lateral 

 line. Its length is about four inches. It is found principally in Southern 

 Russia, but extends into Austria by way of Cracow, and is found in the 

 Poprad, which is a tributary of the Vistula. 



The second variety, Cottus ferrugineus (Figs. 22, 23), has a more slender, 

 rounder body. Its pectoral fin is smaller, and the anal fin has longer rays : in 



