20 
THE yOYAGE OF H.M.S. CHALLENGER. 
As usual they increase in length from before backward. Their chief peculiarities are the 
large size, smoothness, and the great length of the median peninsula before the canals 
from the processes join (PL II a. fig. 5). 
A slightly opaque granular dej)osit exists outside the canal in the longer process, and 
often also in the smaller, as well as in other parts of the tij). The canals show very 
distinct granules below the fork. The whole of the tip, to a point below the fork, is 
covered with a microscopic shagreen. The arrangement of these dorsal bristles is always 
more lax than that of the ventral. 
The ventral bristles form a dense fascicle with the broad axis of the fan directed 
vertically. The larger bristles are generally dorsal, indeed, when the tuft is viewed from 
the ventral aspect a somewhat regular gradation of the tips is observed, so that the slope 
from below upward is bristled with a continuous series, which the few shorter dorsal 
bristles do not affect. In a lateral view the outline narrows from below upward to 
the long bristles. These are paler than the dorsal, and much more slender (PL IIa. 
fig. 6). The inner border of the long process of the fork has two (or in some three) 
serrations, and the isthmus at the base of the fork is proj)ortionally shorter than in 
the dorsal. The type of both corresponds very closely except that the surface of the 
tip in the ventral does not show the microscopic shagreen. When a bristle is broken and 
left in water the shaft exhibits in its centre a series of obliquely curved lines, and in 
many a number of regular transverse lines occur below the isthmus at the fork, and 
throughout a considerable extent of the shaft beneath. The yellowish oleaginous contents 
of the bristles are well seen after fracture, both externally and in the hollow of the shaft, 
where they sometimes assume a lenticular shape. Mr. W. A. Haswell, B.Sc., who has so 
carefully and skilfully investigated many of the Annelids of New South Wales, describes 
two species of Notopygos ^ in which both dorsal and ventral bristles are quite smooth. 
The dorsal bristles of the present species, Notopygos labiatus, have no serrations, so that too 
much weight need not be attached to this character of Kinberg’s. 
The branchial cirrus arises at the inner border of the bristle-papilla, a little in front 
of the branchia, is pale at the base, but tinted madder-brown throughout the rest of its 
extent. It is covered with rows of long cilia. The dorsal cirrus proper (in the usual j^osition 
behind the papilla) has a madder-brown large basal division and a filiform pale distal 
region, which is constricted just below the soihewhat cylindrical tip. 
In transverse section the body-wall shows the features of the group, besides certain 
definite characters of its own. Instead of the little bifid papillse of the hypoderm of .the 
central dorsal region of the Chloeia from the Mediterranean, this form shows a central and 
two median longitudinal ridges, by the great increase of the central oblique muscles of the 
part. The circular muscular layer (beneath the hypoderm) is also largely developed. The 
nerve-cords are especially large and distinct, and are much less flattened out than in 
1 Proc. Linn. Soc. N. S. Wales, November 25, 1878. 
