136 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



showing an alternation of usually 3-4 tiers of long cells with 1 tier of 

 short cells; conceptacles low, half-immersed, not very prominent, 240- 

 440 fj. in diameter. 



Type : Holotype is a specimen without date or locality in the Lam- 

 ouroux Herbarium, Institut Botanique, Universite de Caen, France. 

 Isotype fragments are on sheet 55422 in HAHF. 



Type locality: Marianas Islands, Micronesia, (saxicolous). 



Mexican distribution: Pacific Baja Calif. — D. 9943, 10484, 

 10-17 miles west of Punta Malarrimo, Bahia Vizcaino, Apr., Oct. 

 Nayarit — Taylor 39-641, dredged off Isla Maria Magdalena, May. 



Although markedly polymorphic in different clumps, and even within 

 a single plant, well-developed examples are readily recognized by their 

 broad lower segments with distinct, coarse midrib. The midrib is usu- 

 ally best seen from below. 



Amphiroa annulata Lemoine 

 Plate 29, fig. 3 



Lemoine, 1929, p. 78, fig. 34, pi. 4, fig. 1. 



Thalli tufted, to 17 mm. high, growing on rocks, shells or nulli- 

 pores, consisting of many erect, branched axes from an inconspicu- 

 ous crustose stratum; branching erect, irregularly multifarious, with 

 narrow angles, primarily dichotomous but with frequent secondary, 

 accessory pinnate branches ; segments cylindrical, simple, or more com- 

 monly forked, somewhat compressed at the forks (200) 250-300 (400) 

 ju, in diameter, usually more slender at the base than in mid-parts, 1-2.5 

 mm. long, prominently annulate throughout, the successive annulations 

 coincident with slight constrictions, apices truncate; genicula incon- 

 spicuous, often scarcely evident without decalcifying, unizonal, rarely 

 coincident with forking; cortex very thin, usually of 1-2 layers of small 

 cells, without secondary growth; medulla with alternation of zones of 

 3-5 tiers of long cells with one tier of short cells ; tetrasporangial con- 

 ceptacles prominent, hemispherical, 250-300 (350) fx in diameter, scat- 

 tered on all sides of the segments ; sexual plants not seen. 



Type: Holotype is a specimen obtained by the St. George Expedi- 

 tion, in the Museum National d'Histoire Naturelle, Paris, France. Iso- 

 type preparations are on slides 1460 and 1461 in HAHF. 



Type locality: James Bay, James Island, Galapagos Archipelago. 



Mexican distribution: Pacific Baja Calif. — D. 9951, 10 miles 

 west of Punta Malarrimo, Bahia Vizcaino, Apr.; D. 10438, 17 miles 



