BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 
469 
south of the cape in exposed situations where they may be expected to find conditions 
approaching those of the north coast. 
*Chzetomorpha melagonium. 
*Laminaria digitata. 
*Plumaria elegans. 
Actinococcus peltzformis (0). 
Gymmnogongrus norvegicus (0). 
Euthora cristata (0). 
The list is as follows: 
| *Rhodymenia palmata. 
*Delesseria sinuosa. 
Melobesia membranacea (0). 
Rhodomela subfusca. | *Lomentaria rosea. 
Another group of species comprises those which range both north and south of Cape 
Cod; many of them are conspicuous in the warm-water sublittoral formation (B). The 
following are prominent: 
Chorda filum. 
*Laminaria Agardhii. 
*L,. Agardhii var. vittata. 
*Ceramium rubrum. 
Polysiphonia atrorubescens (0). 
*P. elongata. 
*P. nigrescens. 
P. nigrescens var. fucoides (0). 
P. urceolata. 
Actinococcus subcutaneus. 
*Ahnfeldtia plicata. 
*Chondrus crispus. 
*Phyllophora Brodizi. 
*Phyllophora membranifolia. 
Agardhiella tenera. 
*Cystoclonium purpurascens. 
*Cystoclonium purpurascens var. 
cirrhosum. 
Grinnellia americana. 
Polyides rotundus. 
Corallina officinalis. 
Hildenbrandia prototypus. 
Lithothamnion polymorphum. 
Melobesia membranacea. 
M. pustulata. 
Chetomorpha linum. 
Cladophora albida var. refracta. 
C. gracilis. 
C. rupestris. 
Ectocarpus confervoides. 
E. fasciculatus. 
E. siliculosus. 
*Desmarestia aculeata. 
*D. viridis. 
*Dictyosiphon hippuroides. 
*Chordaria flagelliformis. 
Leathesia difformis. 
*Ralfsia clavata. 
Finally there is a group of species which are widely distributed in the warm-water 
sublittoral. Chief among them are— 
| *Spermothamnion Turmeri. 
Rhodomela Rochei. 
Cladostephus verticillatus. 
*Antithamnion cruciatum. 
The lists of species in the genera Cladophora and Ectocarpus are undoubtedly far 
from complete, for studies at other seasons of the year would be expected to give many 
additions. It must be remembered that we know nothing of this formation in the lower 
portion of Buzzards Bay and the westerly portion of Vineyard Sound in the winter and 
spring when the conditions are much more favorable for the support of a cool-water 
sublittoral flora. 
The chief factor which determines the cool-water sublittoral formation is the 
relatively low temperature of the bottom water during the summer months. The 
records of the temperatures off Gay Head and Cuttyhunk for the summer, as well as for 
other seasons of the year, are presented in a table on page 450, to which the reader is 
referred. It is probable that the lowest winter temperatures of the bottom water at 
these points fall somewhat below 35°, and that the highest summer temperatures are 
close to 60°. This represents about the yearly range of the bottom temperatures off 
the exposed points of Gay Head and Sow and Pigs, and in general of the extreme westerly 
portion of Vineyard Sound and the deeper water of the lower portion of Buzzards Bay. 
The cool-water sublittoral formation may then be said to endure a maximum tempera- 
ture of about 60° for a short period in midsummer, but to live for most of the year at 
temperatures considerably lower. Its most favorable temperature is perhaps close to 
50° or below. Whether essentially the same formation is present during the winter 
is not known, but it seems very probable. 
