300 C. O. WHITMAN. 
Acetabulum 6 mm. in diameter, circular, and centrally 
attached. 
Annuli 102.—The 5th and 6th annuli coalesce on the 
ventral side; and the same is true of the 7th and 8th. 
Counting on the ventral side, and omitting all that are not seen 
from this side, we find only ninety-three annuli. The first 
would be the 5th and 6th of the dorsal side; and the second, 
the 7th and 8th. Behind the 93rd, which is the last that can 
be seen from the ventral side, there are three more to be 
seen on the dorsal side, the last of which is very imperfectly 
defined. 
Most of the annuli appear double, when the leech is at 
rest. ‘To ascertain the whole number of annuli, it is necessary 
to count from the dorsal side, and to begin with the ring 
bearing the first pair of eyes. There are sometimes one or 
more faint indications of rings in front of this point, but they 
cannot be safely counted. 
Buccal Annuli—the 5th and the 6th, the ventral halves 
of which are united. 
Post-buccal Annuli—the 7th and the 8th, also united 
below. 
Genital Apertures.—The male orifice lies in the posterior 
edge of the 30th annulus (24th counting from the buccals on 
the ventral side), often appearing in hardened specimens, to lie 
between the 30th and the 31st. The vulva lies five rings 
behind the male orifice, in the posterior edge of the 35th 
annulus, in hardened specimens apparently between this and 
the 36th. In specimens obtained from Aomori, both orifices 
were exactly between the above-named annuli. 
The male orifice is located between the 2nd and 3rd 
annuli of the 10th somite ; the female orifice, between cor- 
responding annuli of the 11th somite. 
Clitellum embraces the 9th, 10th, and 11th somites. 
Anus in the 102nd, or last annulus. 
Ocelli, five pairs. The first three pairs form a semicircle 
on the first three annuli, each annulus bearing a single pair of 
eyes; the fourth pair is placed on the 5th annulus, or first 
