164 Proceedings of Royal Society of Edinburgh, [april 4, 
ence might be regarded as of generic value, were it not for the 
correspondence in all other essentials of structure. 
Another point of difference from U. corethrurus concerns the 
genital setse ; not, however, in their general shape, for I find no 
difference in this respect between the genital setae of my TJrochceta 
and those figured by Perrier. But while in U. corethrurus the 
genital setae are confined to segment 20, where they replace the 
ventralmost setae on either side, my species has four pairs of these 
peculiarly modified setae ; they have precisely the distribution 
mentioned by Horst in U. duhia, being found upon segments 1 8-2 1 , 
and occupying the position of the ventralmost setae. 
Inter segmental Septa . — As in so many other species and genera 
of earthworms, the present species exhibits a thickening of certain 
of the anterior mesenteries. There are four of these specially 
thickened mesenteries, the first of which immediately follows the 
gizzard; the last forms the posterior boundary of segment 10. 
It is in the segments bounded by these thick mesenteries that the 
spermatbecae lie. 
The hindermost of these thickened mesenteries, as already stated, 
marks off the 10th from the succeeding segment ; the arrangement 
of the mesenteries in front of this does not correspond exactly with 
the external segmentation. The posterior spermatheca lies in a 
segment which is bounded anteriorly by the last but one of the 
thickened mesenteries, and posteriorly by the last of these ; exter- 
nally, however, this segment is distinctly separated by a cross furrow 
into two segments; and, moreover, the difference between the 
external and internal segmentation is not only marked by a cross 
furrow, but also by what is more important, namely, a distinctly 
double row of setae. 
In the median ventral region of the body there are traces left 
of the mesentery which should divide the 9th from the 10th 
segment on either side of the nerve cord; and symmetrically dis- 
posed in relation to the nerve cord and to each other is a muscular 
band, which is attached above to the posterior stout mesentery, and 
below to the furrow which marks the division between the 9 th 
and 10th segments. The stout mesenteries are everywhere at their 
insertion on to the body wall divided into separate muscular bands, 
two of them only being left between segments 8 and 9. 
