206 
are so fragmentary as to preclude detailed comparison. 
Besides the points mentioned above as common to the 
three limnivorous families, the Opheliide and Areni- 
colide agree in the character of their nephridia and in 
their non-ganghonated nerve-cord. The main points of 
difference between them are (1) the shape of the body; 
(2) the skin, which is not sculptured and sub-divided into 
annul in Opheliide; (3) there are no branched gills and 
no hearts in Ophelude; (4+) the parapodia, on many of 
which, in Ophelia, there is a filamentous dorsal cirrus. 
On comparing the Arenicolide and Maldanide the 
differences are again more obvious than the resemblances. 
They agree in the general form of their parapodia, in the 
small number of nephridia and gonads, and in the simple 
brain and ventral nerve cord with uniform covering of 
ganglion cells. They differ in habit, the Maldanide 
have few but long segments, they have no gills and no 
otocysts, and the tail segment is specialised. The ali- 
mentary canal of Maldanide is simple and bears no 
special glands, and there are no hearts. The genus 
Branchiomaldane presents features some of which are 
intermediate between these two families. 
The anatomy of the Chlorhemide is imperfectly 
known, but there appear to be no points in which they 
approach the Arenicolide. The former family differs 
from the latter in its set, septa, nephridia, median heart, 
the processes of the prostomium and the ganglionated 
nerve-cord. The Sternaspide are still further removed 
from the Arenicolidee by the peculiar arrangement of their 
cills and sete, the presence of ventral shields, special 
genital ducts, coiled alimentary canal and only a single 
pair of nephridia. 
It may be eoncluded that the Arenicolide form a 
act family clearly distinguished from the neigh- 
lo} 
comp 
