166 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



1. Tetrasporangia associated with paraphyses in superficial nema- 

 thecia or sori ; thallus little or moderately calcified, mostly below 

 2 



2. Cells on the lower side of the thallus in simple or dichotomously 

 branched parallel rows Peyssonnelia 



2. Cells on the lower side of the thallus forming small fan-shaped 

 groups Cruoriella 



HILDENBRANDIA Nardo, 1834 



Plants horizontally expanded, widely spreading, the lower side 

 strongly adherent, composed of a horizontal filamentous layer from which 

 arise erect cell rows to form the upper layer of the plant, the whole 

 strongly united to a firm though thin uncalcified crust; tetrasporangia 

 irregular in division or zonate, borne in sunken conceptacles which dis- 

 charge by a pore. 



KEY TO SPECIES 



1. Fresh-water streams; thallus very thin, drying rose red H. rivularis 



1. Marine species 2 



2. Thallus thin, brownish red drying bright to dark rose red; con- 

 ceptacles relatively shallow with a relatively open pore, the tetra- 

 sporangia irregularly divided H. Prototypus 



2. Thallus up to 1-2 mm thick, drying dark purplish red or black- 

 ish ; conceptacles rather narrow and 200-800 [x deep with a pore 

 100-150 fji wide; tetrasporangia zonately divided . H. occidentalis 



Hildenbrandia rivularis (Liebmann) J. Agardh 



Colombia : Choco, forming a thin red film on rocks in a fresh-water 

 stream above high tide influence, Bahia Utria, no. 34-505, 14 Feb. 1934. 



Hildenbrandia Prototypus Nardo 



Taylor 1937, p. 257, pi. 36, figs. 9, 10. 



Mexico: Is. Revilla Gigedo, very abundant on rocks in higher tide 

 pools. Sulphur Bay, I. Clarion, no. 39-7, 16 Mar. 1939. Nayarit, on 

 rocks and pebbles in very heavy surf, I. Maria Magdalena, Las Tres 

 Marias, no. 39-675, 9 May 1939. Guerrero, abundant on rocks. White 

 Friars Is., off Ba. Petatlan, no. 34-563B, 2 Mar. 1934. Oaxaca, abun- 

 dant on large granite boulders, intertidal, Ba. Tangola-Tangola, no. 34- 



