31 
TAB. LXXVI. 
HIRUDO circulans. 
Gen. Char. Body oblong, truncate at both ends, 
unarmed, cartilaginous, and moves by dilating 
the head and tail, and contracting into an arch.— 
Turton. 
Spec. Char. Oblong, acuminated towards the head, 
convex above, flat beneath, dull red. 
I found this curious Leech on the Thames side in 1800 , 
and I believe it is not very rare. It is excellent for showing 
the circulation of the blood, through a curiously disposed 
set of vessels about three quarters of its length, at one pulse. 
The head seems to have two eyes, and the mouth is apparently 
underneath, being a small roundish aperture. The animal 
is about an inch long when stretched out, and only half an 
inch in length when contracted. It is very flexile in its 
motions ; and, like all leeches, it can attach itself by its 
posterior end, but at the head has less of that adhesive 
property, and very seldom uses it. The upper side is 
convex, and obscurely striated across. The under side is flat, 
and appears nearly as in the magnified figure in the middle 
of the plate. 
