30 
THE VOYAGE OE H.M.S. CHALLENGES. 
and an enter of two filaments. When fully formed the organs differ from those of the 
previous form by their greater size and more evident divisions, features borne out on 
microscopic examination. The processes are larger and longer, as well as more distinctly 
lanceolate at the tip, whereas in the former case they are blunt. The branchiae are 
continued to the posterior end. 
In examining the dorsal bristles, a feature at once strikes the observer, viz., their 
greater translucency and much more flexible nature. The bifid kind (PL IIIa. fig. 10) have 
somewdiat larger shafts than in the former examj^les, and the serrations on the inner 
side of the tip are less distinct. The serrated kind (PL IIIa. fig. 1 1 represents an average 
specimen) is not marked by distinct lines or grooves toward the tip as in the previous 
form, and the teeth are less prominent. These bristles seem to be more numerous in 
the tuft than in the typical Eurytlioe 'pacijica. Another feature is the great prominence of 
the smooth curved form (PL IIIa. fig. 5) in the foregoing specimens, and their comparative 
paucity and slenderness in this. 
The ventral bristles are on the whole more translucent, and have the tips more dilated 
than in Eurytlioe pacijica proper. One of the average bristles from the anterior third of 
the body is shown in PL IIIa. fig. 12, though it has to be mentioned that the number of 
serrations on the inner edge of the tip is sometimes three or four in the anterior feet. If 
the bristle is slightly turned round the tip appears narrower, so that there is lateral 
flattening. The hastate spine (PL IIa. fig. 14) is somewhat larger than in the previous 
form. The elongated series, corresponding to PL IIIa. fig. 8, is also present, and closely 
approaches the latter. The resemblance in the characters of the bristles is striking, and 
it has been thought unnecessary to make specific separation. 
The nerve-cords have the same relations as in the preceding form, and the alternation 
of the ventral longitudinal muscles is even more apparent. This alternate passage invurd 
and outward of the ventral longitudinal muscle is noteworthy. A small canal exists in 
the central line of the hypoderm. It is interesting to find the canal independent of the 
nerve-oords. 
Hipponoe, Audonin and Milne-Edwards. 
Hipp>onoe gaudichaudi, Audouin and Milne-Edwards (PL I. fig. 5; PL IV. fig. 3; PL 
IIIa. figs. 13-17). 
Elabitat. — Several examples occurred on a log at the surface of the sea, 100 miles 
north of Bermuda, 28th May 1873. Another was found adherent to Lepas fascicularis 
on the surface of the North Pacific, 6th July 1875. 
This form certainly presents a very considerable divergence from the Amphinomidse 
in external appearance. The body is much more flattened, somewhat fusiform in outline, 
and composed of about thirty-two boldly-marked segments, including head and tail. 
The length of the largest specimen is 24 mm., and its breadth fully 5 mm. 
