THE MILLERS THUMB 75 
There are two or more marine species of Cottus found on 
the British coasts, but there is only one fresh-water species in 
reanii Europe, although two well-defined and constant 
Thumb varieties occur on the Continent, distinguished as 
(Cottus go). microstomus and ferrugineus. With these we have 
no concern in this place, having to deal only with the 
curious little fish which is such a familiar denizen of the 
shallow parts of our rivers, and, indeed, of the most 
insignificant rivulets. 
The miller’s thumb is an ungainly creature. Its utmost 
length is about five inches ; the broadest part of its person 
being across the head and gills, equal to about one-fourth of 
the entire length of the fish. The eyes are on the top of the 
head, as best fitted for the ground-haunting habits of their 
owner, and have a greedy, sinister aspect. Each of the 
foremost gill-covers carries a stout spine, an armature which 
sometimes proves fatal to birds which try to swallow these 
fish, for the miller’s thumb, when he finds himself in jeopardy, 
inflates his operculum, spreads abroad his great pectoral fins, 
and tries to look as terrible as possible. These same pectoral 
fins are no unpleasing feature, developed, as they are, into 
broad and rounded fans. The ventral fins are reduced to the 
nature of supports to the fish as it lies upon the ground. 
The first dorsal fin has a rounded outline supported by eight 
rays, and is both lower and much shorter than the second, 
which has about seventeen rays. The ventral fin is greatly 
developed, containing about thirteen rays. Altogether the 
miller’s thumb seems more amply provided with means of 
propulsion and balancing than are many other fish which have 
more use for them. 
In colour this fish is somewhat variable, but the skin, which 
is without scales, has a grey ground colour, tending to brown 
on the back spotted with darker brown. The sides are streaked 
or mottled with brown, and this hue sometimes extends over 
the belly, which is whitish. The male is generally darker 
