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PACIFIC SCIENCE, VoL VIII, July, 1954 
tances separating the islands together with 
restriction of the consideration to just two, or 
few, genera leaves the impression of zonation. 
One of the first explanations for these in- 
dications of exclusiveness in range to come to 
mind is that Sargassum only occurs around high 
islands ( igneous substrata, drainage, etc. ) . 
However, both Lemmerman (Bot. Jahrb. 34: 
607-663, 1905) and Reinbold-Itzehoe 
(Naturw. Ver. zu, Bremen, Abhandl. 16: 287- 
302, 1899) record Sargassum from Laysan (Ha- 
waiian group ) , which probably must be classed 
as a low island (carbonate substrata, etc.). It 
is similarly found about low islands in the 
Atlantic. An interesting test of this hypothesis 
would be analysis of the presence or absence of 
these genera in the Marquesas Islands, which 
are a group of high islands as near the equator 
as are the low Phoenix and Line islands. 
Even though Sargassum, and not Rhipilia, 
might occur in the Marquesas, one is still left 
with the interesting observation that there is 
an area in the Central Pacific (i.e., between 
about 141°W and 165°E, and between about 
16°N and 16 °S) in which Sargassum has not 
yet been reported (Samoa is at about 14°S) 
and outside of which, latitudinally, Rhipilia 
geppii has not been found. This same area is 
one of relatively inactive, or "dead,” reefs. 
This central region may prove to be an im- 
portant biotic province. The relatively great 
development of such species of the genus 
Porolithon as P. gardineri, P. aequinoctiale, and 
especially P. onkodes in this area supports this 
hypothesis. 
Sargassum is readily noted and frequently 
collected, if present, even by chance visitors 
who are not primarily phycologists. Rhipilia, 
however, grows in relative seclusion, is usually 
less than 5 centimeters tall, and is, therefore, 
not frequently collected by others than phy- 
cologists. Rhipilia geppii grows among dead 
coral branches (e.g., between Pocilopora 
branches just behind actively growing lagoon 
reef edges and usually a decimeter or two below 
the upper general level of the coral surface). 
As a rule it looks like clusters of poorly formed 
dark green, felt-like, noncalcareous blades on 
indistinct stems. 
Specimens of Sargassum from any other places 
in the Central Pacific, as well as notices of 
collections of Rhipilia, could be valuable con- 
tributions toward providing the means of a 
better explanation for this apparent mutual 
range exclusion phenomenon. - — Maxwell S. 
Doty, Department of Botany, University of 
Hawaii. 
Substitute for an Invalid Generic Name 
in the Crustacea 
Attention has been called to the preoccupa- 
tion of the generic name Mesocaris Edmond- 
son (Bernice P. Bishop Mus., Occas. Papers 10 
(24): 13, 1935) by Mesocaris Ortmann 
(Ergebn. Plankton-Exped. 2 (Gb): 73, 82, 
1893). To validate the genus of 1935, I 
propose to substitute the name Antecaridina 
for Mesocaris Edmondson.- — C. H. Edmond- 
son, Bernice P. Bishop Museum, Honolulu, 
