176 Proceedings of Boy al Society of Edinburgh, [april 4, 
It is perfectly clear that the above-quoted specific diagnosis is 
entirely insufficient to discriminate the species from many other 
Perichcetce ; hut an examination of the specimen itself leads me to 
believe that it is a distinct species. I am unable to give any 
anatomical description, hut the worm exhibits an external character, 
overlooked by Baird, which is of some value as an aid to dis- 
criminating the species. The male genital pores are as usual 
situated upon the 18th segment of the body, and at some distance 
from each other; the 17th and 19th segments are each furnished 
with a single median genital papilla placed exactly in the centre 
of the segment, and therefore interrupting the line of setae. The 
number and arrangement of the genital papillae seem to he, so far 
as our knowledge goes, good characters for discriminating the dif- 
ferent species of Perichceta ; although the number is apt to vary 
somewhat (see p. 171) at different stages of maturity; the number 
of papillae in the present species would have to he very largely 
increased to come up to the number which are characteristic of 
Perichceta newcombei (p. 171), the only other species of Perichceta 
which has genital papillae in the median ventral line on the 17th 
and 19th segments. 
Explanation of Plate V. 
Fig. 1. Acanthodrilus dissimilis. 
Fig. 2. Acanthodrilus neglcdus. 
Fig. 3. Neodrilus monocystis, section through prostate; m, muscular duct; 
gl, glandular region. 
Figs. 4-9. Urochceta, sp. 
Fig. 4. Median longitudinal section through glandular appendix of nephri- 
dium; d, glandular cul-de-sac; c, epithelial lining; b, muscular region; 
a , “sphincter” surrounding aperture; m, mesentery. 
Fig. 5. Transverse section through glandular appendix and a portion of 
nephridium ; n, nephridial tubule ; c, d, regions similarly lettered in 
fig. 4. 
Figs. 6, 7, 8. Sections in various planes through nephridial funnel; p, peri- 
toneal cells; p g, peculiar agglomeration of peritoneal cells in the 
funnel. 
Fig. 9. Transverse section of a nephridial tubule from hinder end of body; 
c, peritoneal cells; b, blood corpuscles; n, nephridial tubule. 
Fig. 10. Perichceta newcombei, ventral aspect. 
Fig. 11. Perichceta upoluensis, ventral aspect. 
Fig. 12. Spermatheca of last species. 
