18 COLLINS AND HERVEY. 



the upper a subspherical gonidangium, containing gonidia, 5-6 fj. 

 diam., usually 8-12 in number; the lower cell obconical with flat or 

 concave upper surface, contents bright blue-green; wall thick, some- 

 what lamellate. 



On older parts of fronds of Spermothamnion gorgoneum and Cera- 

 mothamnion Codii, which grew on Codium decorticatum, in company 

 with Xenococcus Schousboei, Lyngbya Meneghiniana and other small 

 algae. The cells are always scattered, never forming cushion-like 

 masses, as is the case with most species of Dermocarpa. The general 

 appearance of the plant is not unlike that of some small species of 

 Codiolum, except for the shade of color, and that the colorless stipe 

 is shorter. 



2. D. PRASINA (Reinsch) Bornet & Thuret, 1876, p. 75, PL XXVI; 

 P. B.-A., No. 2051. Sphaenosiphon prasinus Reinsch, 1875, p. 73, 

 PI. XII. Not D. prasina P. B. A., No. 1, which is D. Farlowii Borgs. 

 On Catenella Opuntia var. pinnata generally. 



XENOCOCCUS Thuret. 



X. SCHOUSBOEI Thuret in Bornet & Thuret, 1880, p. 74, PI. 

 XXVI, figs. 1-2; P. B.-A., No. 2052. On Lyngbya confervoides, in 

 ditch back of Shelly Bay, Aug., Collins. Cells mostly separate 

 and exactly spherical ; but sometimes closely packed and compressed. 



Var. PALLIDA Hansgirg, 1889, p. 5. On algae on roof of cave, 

 Gravelly Bay, April, Collins. What may be a species of Xenococcus 

 with minute cells was found on Oedogonium from Devonshire marshes, 

 but could not be specifically identified. 



FAMILY OSCILLATORIACEAE. 



SPIRULINA Turpin. 



1. Trichome rose-color. 1. S. rosea. 



1. Trichome aeruginous. 2. 



2. Trichome less than 1 yu diam., spiral loose. 2. S. tenerrima. 



2. Trichome over 1 n diam., spiral close. 3. S. subsalsa f. oceanica. 



1. S. ROSEA Crouan ex Gomont, 1893, p. 273. Forming a pinkish 

 film on Amphiroa between tide marks, North Shore, Sept., Collins. 

 *2. S. TENERRIMA Kiitzing ex Gomont, 1893, p. 272; Kiitzing, 



