Three New Species of Hirudo, 319 
tends its head to a point at the greateít diftapce from the tail 
where it adheres; then bringing its tail into contact with its head, 
it contracts itfelf into a hemiipheric form, and by this mean 
moves very fait, | 
It has alfo another action in which it refembles the larvæ of the 
geometra, When difturbed, it fixes itíelf by its tail, and then, 
raifing itfelf perpendicular to the plane of pofition, moves its head 
from fide to fide, {upported merely by the expanded adhefive orb 
of the tail. 
I found this with the preceding, ones, but it feems a rarer 
qe 
Obfervaiton.—' The Hirudo a/ba and nigra, as alfo iid ridi of 
Dr. Shaw, appear to me not rightly referred to this genus, as they 
by no means agree with the Linnean definition. Corpus oblongum 
ore caudaque in orbiculum expandendis Je promovens. The motion of 
thefe three fpecies is uniform and equable, nor do they poffefs 
that orbicular adhefive expanfion of the head and tail which con- 
ftitutes the effential diftinétion of the genus Hirudo. Qu. Are 
they fufficiently diftin& to conftitute a new genus? 
ADDITIONAL NOTE, 
By Dr. SHaw. 
THE Hirudo nigra of Mr. Kirby I believe to be the Planaria 
fufca of Pallas and Gmelin, Syft. Nat. p. 390. 
The Hirudo alba of Mr. Kirby is probably the Planaria laëtea of 
Gmelin, defcribed by Müller in the Zoologie Danica; and in the 
Jt, Gothl, it is confidered by Linnaeus as a Hirudo 3 
^ 
