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PACIFIC SCIENCE, Vol. VIII, October, 1954 
Fig. 10. a, Caulerpa serrulata: A small part of a plant, X 1.5.3, Caulerpa vertkillata: A small part of a plant, X 5. 
c, Caulerpa racemosa var. macrophysa: A small part of a plant, X 1.5. 
This minute species is similar in size and 
epiphytic habit to Derbesia neglecta Berthold 
(see B0rgesen 1925: 105, figs. 43-44; Hamel 
1931: 400), but differs in its solitary habit, 
regular dichotomous branching above a prom- 
inent main axis, and pronounced attenuation 
to the tips. Inasmuch as the present material 
is sterile, there remains some doubt as to the 
generic position, though the vegetative char- 
acters point toward Derbesia. 
Since the above was written this species has 
been found growing abundantly on old Gal- 
axaura at Binners Cove, Isla Socorro, in the 
Revillagigedo Archipelago (Dawson 12133a, 
Nov. 19, 1953). 
Key to the Species of Caulerpa 
1. Thalli small, less than 1 cm. high 2 
Thalli over 1 cm. high 3 
2. Branching rather sparse, irregular 
C. fastigiata 
Primary branching approximate, pinnate, 
subopposite C. ambigua 
3. Ultimate branchlets very slender, terete, 
in subverticillate fascicles. C. verticillata 
Ultimate branchlets coarse, not terete. .4 
4. Branches + — contorted, coarsely serrate 
C. serrulata 
Branchlets terminally inflated 
C. racemosa var. macrophysa 
Caulerpa fastigiata Montague 1845, pi. 2, 
hg. 3 (Cuba); B0rgesen 1913: 118, fig. 93; 
Vickers 1908, part 1, pi. 36 
Fig. 9g 
LOCAL DISTRIBUTION: Forming small mass- 
es of filaments a few cm. in extent, Sta. 4 
(11157). 
Caulerpa ambigua Okamura 1897: 4, pi. 1, 
figs. 3-12 (Ogasawarajima); Okamura, 
leones 3, pk 139; Eubank 1946: 410, pi. 
22, figs, a, b; Egerod 1952: 369 
Fig. 9/ 
LOCAL DISTRIBUTION: A few small plants 
less than 1 cm. high attached to a coral head 
dredged in 2-3 m., Sta. 2 (11366a). 
Caulerpa verticillata J. Agardh 1847: 6 
(Atlantic Mexico) 
Fig. 10^ 
LOCAL DISTRIBUTION: Occasional on inter- 
tidal sand flats, Sta. 4 (11161). 
