152 NOTES ON RANGE IN DEPTH OF MARINE ALGÆ. 
€ pem the Abrolhos shoal, in 40 fathoms, in lat. 18? 11" S., long. 
3' 15" W., thirty miles from the nearest part of the coast of 
cdd Most of it consisted of a species of Melobesia, much decayed, 
but partly also fresh and entire ; adhering to it, growing on it, in fact, 
there is a solitary specimen of an Alga of bright crimson. On exami- 
nation I had no hesitation in referring it to the genus Peyssonelia. It 
is not very prudent to describe supposed new species from solitary 
examples ; nevertheless, as it seems to differ from others known to me, 
and being of interest in relation to the subject, it may be legitimate to 
record it under the provisional name Peyssonelia abyssicola, sp.n.* If 
a single cast of the sounding-lead did such good service, how much 
more would the dredge accomplish on this Abrolhos shoal $ 
Finally, it is worthy of notice, that species which reach the lowest 
depth where Algæ vegetate are chiefly Rhodosperms ; next in order 
the olive-coloured. The Chlorosperms prevail in the littoral and 
upper part of the laminarian zones. 
Diatomacee are usually considered to rank among the lower forms 
of Algæ. I may close with a brief reference to their range. Although 
some few species have been certainly brought up from the greatest 
depths reached by the dredge, it does not necessarily follow that they 
live and propagate there. Many of the marine species adhere to the 
higher forms of seaweeds, and necessarily have a limited range; while 
not a few of the free species occur at or not far below the surface. 
Along with the Delesseria already mentioned as growing at 80 fathoms, 
I only detected three Diatoms, viz. Melosira marina, Coscinodiscus 
radiatus, and C. eccentricus. These minute organisms are so inde- 
structible, so abundant, and widely diffused, that it is not surprising 
to find them in matter dredged at various depths. The Melobesia 
from the Abrolhos shoal yielded at least a dozen species, but I cannot 
positively assert that they were living. 
It is to be hoped that in future more attention will be paid to this 
subject. Exact records of depth will add to the interest pertaining to 
the Algæ procured, besides contributing to a department of inquiry very 
much overlooked ; in this respect zoologists are far ahead of algolo- 
gists. 
* Peyssonelia abyssicola. aa circular, faintly zoned concentrically, sub- 
g 
tomentose beneath, about half an inch in diameter; colour bright red; upon 
Lithot thamnium mamillare (Melolesia ane. Harv. arvey). 
