196 Sitst Annual Report 
collection ‘‘is a discovery, or rather rediscovery. This species was 
credited to our coast nearly forty years ago, but so far as I know has 
not been seen since.’’ 7 
Calothrix parasitica (Chauv.) Thuret 
(Figure 105) 
Commonly parasitic in Nemalion lubricum. 
Calothrix contarenii (Zau) B. and F. 
Colonies of this species are occasional on exposed rocks almost 
to high tide mark. 
Figure 106. Chaetomorpha aerea (Dillw.) Kurtz 
Calothrix fasciculata Ag. 
Colonies common on exposed rocks almost to high tide mark. 
This and the preceding species form a slippery covering to the 
rocks that render them very treacherous for the pedestrian. During 
low tide on a hot day this little alga is seemingly completely dried 
out, and must be subjected to great heat, but always recovers prompt- 
ly with the next tide. 
