390 
BULLETIN OF THE BUREAU OF FISHERIES 
6.0-millimeter stage. — Total length, 6.0; standard length, 6.6; length to vent, 2.5; 
length of head, 1.2; diameter of eye, 0.35; greatest depth before vent, 0.9; depth 
behind vent, 0.35 millimeter. Myomeres, 10 to vent plus 22 (23) behind. Embryonic 
marginal fin fold originating over fifth myomere behind head (in kumlieni over first), 
with considerable concentration indicating formation of caudal rays in the still 
lophocercal tail (much more development than in kumlieni of 7.2 millimeters) ; large 
unrayed pectorals reaching halfway to vent; very broad head with longer and more 
pointed snout than in kumlieni. 
Pigmentation. — Several chromatophores occur on ventral surface shortly before 
vent (but not as large nor stellate as in kumleini ), and a conspicuous series of rather 
Figure 133 . — Coitus bairdii bairdii, 6 millimeters 
large rounded spots is evident along ventral surface of tail to caudal (very few, if any, 
small chromatophores in kumlieni of like size). 'The body is otherwise colorless. 
57. Cottus cognatus Richardson. Muddler; miller’s thumb; northern sculpin. 
RECORD OF CAPTURE 
During August, 1928, from the New York State line around the eastern end of the 
lake to Tecumseh Shoals on the Canadian side, specimens of this northern stream 
species were taken in small numbers but rather generally in Petersen and Helgoland 
trawls from 16 to 23 meters. C. cognatus had not been recorded previously in Lake 
Erie. 
DESCRIPTION 
The young of this species closely resemble C. bairdii kumlieni in their rather 
short bodies, with gill membranes attached to the isthmus, but differ in having pelvic 
fin ray count I, 3. 
18.0-millimeter stage. — Total length, 18.0; standard length, 14.0; length to vent, 
8.0; length of head, 5.0; snout, 1.2; diameter of eye, 1.33; greatest depth before vent, 
3.3; depth behind vent, 2.4; length to dorsal, 5.6; to anal, 8.5 millimeters. Myomeres, 
10 to vent plus 19 behind. Dorsal VII, 17 ; anal 12. Body short and stout; snout not 
