BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 24. AFD. IV. N:03. 13 
in the main we may say that the distance between the eyes 
is greater in OC. gobio than in OC. poecilopus, nevertheless we 
cannot distinguish the species on the ground of this charac- 
ter, which, moreover, is always a matter of doubt, on account 
of the difficulty of taking exact measurements of the eye. 
JEITTELES also remarks that in this respect the variations 
are considerable. 
The preopercular spine. 
LILLJEBORG also mentions this character, given by HECKEL, 
saying that this spine is very slightly curved in OC. poeci- 
lopus, while in OC. gobio it is much more curved, turns up- 
wards, and is very sharp-pointed. CoLrLEtt seems to lay com- 
paratively great stress upon this character. Thus, in a short 
description of C. poecilopus from the lake Mjösen, which ap- 
peared in »Om Norges Fiske i Aarene 1875—1878» in Chri- 
stiania Vidensk. Selsk. Forh. 1879, he shows that some cha- 
racters mentioned by other authors are not constant, but that 
»the spines of the gill-cover are always constant and in their 
character easy to distinguish from those of OC. gobio». It is 
a fact, however, that the spine in OC. gobio is usually more 
strongly developed and more curved; but this is a rule to 
which we have found many exceptions. JEITTELES also rightly 
says: »Die Grösse, Gestalt und Anzahl der Stacheln an Vor- 
deckel lässt sich ganz und gar nicht als Unterschied beniätzen.> 
The different length of the pectoral fins. 
Moreover, according to HEcKEL, the pectorals are longer 
in C. gobio, reaching to the beginning of the second dorsal 
fin, while in C. poecilopus they are shorter. 
C. poecilopus. | 0. gobio. 
| - 
: | 71 45,2) 57,5) 76,1) 42,5| 57,9) 75,5 
Length of the body in millimetres (average) EL sr Hö så ; få 3 
19 | 43,4) 62,7 76,1| 42,4/58 | 75,8 
Length of the Bisenalds in ;R of the '"Jenöth [3] 20,9) 2 glosalasorueer | 
of the body NOS 7] 27 [ISA RS i ” 
Le | 20,8| 22,0] 21,5| 21,3) 22,3) 21,9 
