33 
LITHOTHMX, A NEW GENUS OF CORALLINE. 
By Dr. J. E. Gray, F.R.S., etc. 
Lamarck and Lamouronx divided the Corallinse into genera aceordin 
to the form of the frond-joints. More recently, Decaisne and Harvey 
have characterized the genera by the form of the fruit, whether it was 
like an urn in shape or like a pustule with a central perforation. 
Both these characters are good, and when studied together, as they 
are used by Areschoug and Agardh, they 
afford the means of dividing the species into 
very natural groups, but in most of these 
groups there are species which combine the 
characters in such a manner as to make it 
difficult to determine to which genus they 
are most nearly allied. 
The new form belongs to the group of 
genera having the fructification in the form 
of small pustules on the side of the frond, 
like Amphiroa of Areschoug, which contains 
the genera Euamphiroa and Arlhrocardia of 
Kiitzing, Amphiroa of Lamouroux and Kiitz- 
ing, and Ewytion of Harvey. 
^ The genus may be thus defined, and named LlTHOTHRIX. Frond 
pinnate; joints cylindrical, short, scarcely defined; upper joints rather 
compressed, two-edged; branches simple, cylindrical, pinnate or sub- 
verticillate, generally one from each of the two or four sides of the stem. 
Ceramidia pustuliform on the sides of the joints of the upper part of 
the stem, or of the joints of the lower part of the branches. 
Lithothrix Aspergillum. Frond pinnate or subverticillate ; branches 
simple, opposite or verticillate, cylindrical, indistinctly jointed ; upper 
part of the stem compressed, broader, bearing the pustules on the 
sides ; joints shorter than broad j nodes slightly indented. 
Hab. Vancouver's Island, Dr. C. B. Wood, 1861. 
This Coralline is very unlike any that I find described in the various 
essays on tins group of Algae. It was one of the interesting species 
found by Dr. C. B. Wood, in Vancouver's Island, in 1861, and sent 
to Sir W. Hooker for the Kew Herbarium. I have also a specimen 
from the same locality. 
Lit ho fh rix A sp erg ilium. 
a. complete plant. 
b. portion magnified. 
v OL. V. [FEBRUARY I, 1867.] 
D 
