560 
MR. H. N. RIDLEV ON THE 
Diadem a. saxatile, L. 
Two specimens from pools at Morro do Chapeo. 
Tripeehstes esculentus, Leslie. 
Very plentiful in rock-pools in Sponge Day, sometimes almost 
filling a small pool. 
Ophiura cinerea, M . Tr . 
Common under stones, north side. 
Ophiacantha sp. 
A very small specimen with the preceding. 
Ophiocoma pumila, Lutk. 
Young specimens. 
Ophiocoma echinata, Ag . 
A single specimen from Portuguese Pay. Quite unknown to 
our guide, so it is probably rare here. 
OLIGOCHiETA. 
By W. Blaxland Benham, D.Sc. 
On Pebruary 2, 1889, I received a tube of small worms, which 
had been collected by Mr. H. N. Ilidley in the island of Fer- 
nando Noronha, with the request that I would identify them. 
I gladly undertook to do so, and obtained permission to open 
the worms, if necessary ; for it is now admitted that in most 
cases it is almost impossible to pronounce with certainty on the 
genus of an Earthworm from external characters alone ; and 
although in some cases external characters may point to some 
particular genus, yet it is not always safe to rest content with 
such an indication, and we must examine the internal anatomy 
in order to be sure of the point. 
The tube which I received contained six small, ill -preserved 
worms, one of which was a Polycbaete, which I did not further 
examine. Of the remaining five, the first (which I will call A) 
was of rather an earthy-brown colour and measured 4 inches 
in length ; the second and third were similar in colour and 
general appearance, but were only about 2 inches long; the 
fourth (B) was of a much darker tint, and was reddish brown in 
