462 JOHS. BOYE PETERSEN 



the sheaths were comparatively distinct; but I have not been able to detect 

 in the deficient material any sheath containing more than one trichome. 

 Nevertheless I feel convinced that the form observed is identical with the 

 named species. 



Area of distribution: The shores of the Bermuda Islands, Guadeloupe 

 and Australia. 



Fam. Scy tonemaceae . 



Microchaete Thuret. 



M. vitiensis Askenasy. 



EoRXET et Flahault, Revision HI, Ann. sc nat. 7' ser. T. V, 1887, p. 85. 



The plant formed a red layer (c. 5 mm. in diameter) in Zonaria varie- 

 gata. The filaments were 8 — 9 a in diam., the trichomes 6 — 7 a. The cells 

 are quadrate or slightly shorter than the breadth. The heterocysts are only 

 basal. 



Area of distribution: Pacific Ocean. 



Fam. Ri vulariaceae. 

 Calothrix Ag. 



C. Crustacea Thuret. 



BoRNET et Thuret, Notes algologiques I, p. 13, pi. 4; Bornet et Flahault, 

 Revision I, 1. c, T. Ill, p. 359. 



I found this species among Sphacelaria sp. in a sample chiefly containing 

 Hypnea Esperi, and the Calothrix must undoubtedly have grown on the stone, 

 being removed from this together with the larger algae. The diameter of the 

 threads was 17,6 -23 ij., of the trichomes 11 — 17 ;J.. Numerous heterocysts 

 were present, basal as well as intercalary. As the apices of the trichomes 

 unfortunately were wanting in all the observed specimens, a confusion with 

 C. rectangularis S. et G. (Setchell and GARDNER, The marine algae etc. I. 

 Univ. Calif. Publ. Vol. 8, No. i, p. 100, pi. 6, fig. 21) was not excluded, the 

 distinguishing character of the two species being exactly the length of the 

 apical hairs. However, as the observed CalotJirix was provided with numerous 

 heterocysts of different form, these being sometimes cylindrical, sometimes 

 depressed, almost disc-shaped, and as the latter form evidently does not occur 

 in C. rectangularis judging from the description and the figures in Setchell 

 and Gardner 1. c, I am of the opinion that the found specimens ought to 

 be identified with C. Crustacea. In one respect only they apparently differred 

 from this species: the threads were not swollen at the base but on the con- 

 trary slightly attenuated towards the base. 



Area of distribution: Atlantic Ocean, Mediterranean Sea, Pacific Ocean. 



