16 ANDERSSON, COMPARISON OF COTTUS POECILOPUS WITH COTTUS GOBIO. 
the base of the caudal fin, there usually exists, nevertheless, 
a distinct broad groove, which as a rule runs straight along 
the middle of the tail. Nevertheless we meet with some 
intermediate forms which render even this character unim- 
portant as a specific distinction. 
The second character given by GÖUNTHER, vViz. that on the 
ground of the different course of the lateral line, is proved 
to be more constant. In OC. poecilopus the lateral line runs 
at about !/s of the depth of the body (measured from the 
ridge of the back); in C. gobio somewhat above the middle 
of the body. 
| IC. poecilopus. | 0. gobio. 
| [EN Mb | 
| > | 45,21 57,5] 76,1] 42,51 57,9) 75,5 
7176 
| Length of the body in millimetres (average) 
4 SP SSR | 82) 19 |48,4| 62,7] 1] 42,4 58 |75,8 
Distance from the lat. line to the 2d D. fin 
in 4 of the distance between the lat. line IC 46, sl 48 10) 49,3) 71,4 70,9] 70,2 
and the beginning of the A. fin . . "19 | 48,8) 47,1] 49,3 75,6| 73,9| 70 
81 474,11 (0, , 
My measurements in the table above show the average 
distance between the lateral line and the second dorsal in 
proportion to that from the lateral line to the first ray of 
the anal fin. The table shows that in this respect a con- 
siderable difference exists between the two forms. In one 
specimen of C. gobio out of 68 the proportion was as low as 
59 z: in all the others it was above 60 Zz. The highest per- 
centage in C. poecilopus was 58,8. Disregarding this exceptional 
specimen of C. gobio, we are then able to state the following 
distinction between the forms, which seems to be fairly con- 
stant. The distance between the lateral line and the second 
dorsal fin is in OC. gobio more, in C. poecilopus less, than 60 4 
of that between the lateral line and the beginning of the anal 
fin. (These measurements are taken in the perpendicular 
through the first anal ray.) 
The different position of the vent. 
As has been mentioned above, GUNTHER points out that 
the vent is differently situated in the two species; but he 
characterizes this difference by distinctions which do not ex- 
