BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 541 
39 
Pyramid Rock 
CHART 271.—Distribution of algae on Spindle Rocks, July 22, 1905. 
The only conspicuous green alga was Ulva Lactuca var. rigida (5), now full grown and forming large 
patches on some of the rocks. There was a very well-defined brown zone just below low-water mark 
(the dotted line) composed of Chordaria flagelliformis (28) and old Scytosiphon lomentarius (26). Ecto- 
carpus confervoides (14) was plentiful on the Chordaria and Scytosiphon. Phyllitis fascia had disappeared. 
Nemalion multifidum (40) fringed most of the rocks at low-water mark, and below was a characteristic red 
zone of Polysiphonia violacea (48) and Ceramium rubrum (43) mixed with the Chordaria, and with Chon- 
drus crispus (49) abundant from 1-5 feet below low water. 
List of algee: Calothrix scopulorum, 1, small patches on barnacles and rocks; Rivularia atra, 2, on 
barnacles; Ulothrix implexa, 3,on Pyramid Rock; Ulva Lactuca var. rigida, 5, abundant on tops of 
rocks; Enteromorpha intestinalis, 7, few patches; Cladophora gracilis, 9, few tufts; Codiolum gregarium, 
12, on barnacles; Ectocarpus confervoides, 14, abundant on Chordaria and Scytosiphon; Scytosiphon 
lomentarius, 26, much old growth; Chordaria flagelliformis, 28, abundant; Mesogloia divaricata, 29, few 
patches; Chorda filum, 31, large patches; Laminaria Agardhii, 33, few groups; Fucus vesiculosus, 35, 
few plants; Nemalion multifidum, 40, abundant; Ceramium rubrum, 43, abundant; Chondria dasyphylla, 
44, few plants; Polysiphonia violacea, 48, abundant; Chondrus crispus, 49, abundant. 
