68 MONOGRAPH OF THE FRESH WATER Til. 
NOTE. 
Since the foregoing pages have been put to press, a new fact touching the 
geographical distribution of Cottus meridionalis, has come to our knowledge, which 
is deemed of sufficient interest to be placed on immediate record here. This spe- 
cies has been found in one of the lower tributaries of the Potomac, in Rock Creek, 
Washington (D. C.). Consequently C. meridionalis occurs in the same hydro- 
eraphical basin as C. viscosus. — ‘ 
It is well known that the aquatic fauna of the Southern States is very different, 
both from that of the Middle and that of the Northern. There are comparatively 
few species which occur throughout the Atlantic States of the Union. Still, faunas 
and floras, although circumscribed within particular provinces or districts, cannot 
be defined in their boundaries by mathematical lines, and we frequently find dis- 
tricts whose lines of demarkation overlap or interdigitate. 
Now the State of Maryland seems to be placed on the limit, between the faunas 
of the Southern and Middle States, a fact which will make the study of its natural 
productions much more difficult, but at the same time of more than ordinary 
interest. 
The locality, Rock Creek, Washington (D. C.), given at page 53 to C. viscosus, 
does not belong to the latter species, to which it was temporarily attributed before 
an examination of the specimens could be made critically. After this was effected, 
an oversight has allowed it to remain there. 
