98 Clark — Itolophytic Plankton of Lakes AtMan and Amatitlan. 



10. Anabaena flos=aqua.- Brebisson. 

 Anabsena flos-aguse Brebisson, "Algues des environs de Falaise. 1835" ; 



EuetzingSp. Alg. 289, 1849; Tab. Phyc. I, 51, Tab. 94, fig. IV, 1845; 



Apstein Sussw-p. 136, fig. 3, 1896; Wolle, F. W. Alg. U. S. 236 (the 



specimens at hand resemble most closely his figure of var. circinalis pi. 



CXCVIII, tigs. 24-26), 1887. 



Very common in all the phyto-plankton from Lake Amatitlan, usually 

 found in the Clatlirocystis-Microcystis scum. 



Order RIVULARIACE.F. 



11. Qloeotrichia natans Thuret. 



Gla'otrichia natans Thuret (Kef. not found) ; Wolle, F. W. Alg. U. S., 24fi, 

 pi. CLXXVin, tigs. 4-20, 1887. 



This appears in one sample of hand-gathered material, among sponges. 

 The forms at hand are hollow jelly spheres about the size of a hazel-nut 

 and much resembling some of the familiar forms of Nostoc. Many of the 

 old, large filaments are brown; but there are many new filaments, some 

 of which are greatly twisted in a rather elongate irregular spiral. The 

 jelly of this species harbors many diatoms and a number of sponge spicules 

 are also present. The plants agree very well with Wolle's description 

 and figures. 



Chlorophyce,e. The Green Alg.e. 



Order HYDRODICTYACFLF. The Water Nets. 



12. Raphidium brauni Nsegeli. 



Raphidium brauni Na-geli in Kuetzing, Sp. Alg. Sill, 1849; Wolle, F. W. 

 Alg. U. S., 198, pi. CLX, figs. 26, 27, 1887. 



Not common ; several specimens, however, found in material collected 

 from the surface about tine hour before dark, Amatitlan, February 10, 

 (Sample 7). 



13. Tetraedron minimum A. Braun. 



Tetrsedron minimum Braun. Alg. Unicell. 1)4, 1855. 



Poly edrium minimum, Wolle, F. W. Alg. V. S., is."), pi. CLIX flgs. 28- 

 :;4, iss7. 



Not common in the plankton; a few examples were observed in sample 

 No. 6, collected at Lake Amatitlan, February 16, 3 p. m. Diameter of 

 cells from side to side 10m; diagonal diameter 12m. 



14. Pediastrum boryanum (Turpin). 



Hierella boryana Turpin, Mem. Mus. Hist. Nat. Paris, L6; 319, pi. 13, 



fig. 22, L828. 

 Pediastrum boryanum Wolle, Desm. U. S., 153, pi. L11I, tigs. 29, 32, 



L884. 



Rare; only one example found, Lodged in a mass of Oscillaria. In the 

 shape of its cells it resembled Wolle's figure 32. Horns »|iiite short. 

 Diameter of colony seen 70fi, cells 20m. 



