ove C. O. WHITMAN. 
narrow rudimentary rings (101 and 102), and even encroaching 
somewhat upon a third (100). This figure represents a speci- 
men obtained at Leipsic. In specimens from Naples, the last 
two rings (99 and 100) show signs of duplicity at their margins ; 
and in one or two cases, it is perfectly evident that both of 
these rings are double, the 99th corresponding to the 99th and 
100th in Hirudo, and the 100th to the 101st and 102nd. 
Allowing that such a correspondence actually exists, we should 
expect to find segmental papillz on both of these rings. They 
are always present on the 99th ring, and in a few cases they are 
quite distinct on the 100th ring. It is safe to conclude therefore 
that Aulostoma has the same number of rings as Hirudo, with 
the difference that in the former the 100th and the 102nd, 
which are non-papillates, are less distinct than in the latter. 
In the Leipsic specimens (fig. 52) the 101st and 102nd rings 
are very distinctly indicated, but not in the same way. It is 
not improbable that the difference here pointed out may have 
the value of a specific distinction. 
The 23rd somite has three rings, but it is noticeable that 
two of these rings (95th and 96th) are much thicker than the 
preceding or the following rings, showing that the abbreviation 
of this somite has not been carried quite so far in Aulostoma 
as in Hirudo. The abbreviation of the 25th and 26th somites, 
on the contrary, is somewhat more extreme than in Hirudo. 
With respect to the anterior abbreviated somites, I am unable 
to point out any differences between the two genera. 
The nephridial pores hold the same positions and relations in 
both cases, and there is only a difference of half a ring in the 
position of the male orifice, which generally occupies the middle 
of the 81st ring,! instead of lying between the 30th and the 31st. 
The number and arrangement of the segmental papille are 
the same as in Hirudo; but the median dorsal and all the 
ventral papille are less strongly developed. In some specimens 
the papille are quite distinct on the acetabulum (fig. 52). 
The denticles are from eleven to fifteen in number, but vary 
1 J have sometimes found this orifice in the anterior edge of the 31st ring, 
very near the line dividing this from the preceding ring. 
