106 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



paraphyses; carpospores 25-32 ju, in diameter; tetrasporangia in small, 

 elevated nemathecia 70-90 /x deep, elongate-ovate, 60-70 ju, long, among 

 short, coarse, non-clavate, simple or branched paraphyses of 4-6 more or 

 less uniform cells 9-10 ja in diameter; antheridia not observed. 



Type: Holotype not designated. The material studied by Grunow 

 from the herbarium of Piccone, later in the herbarium of A. Forti, is i 

 now in the Botanical Institute, Pavia, Italy. A syntype specimen sent 

 to, and studied by Weber van Bosse is in the Rijksherbarium, Leiden, 

 Netherlands. 



Type locality : Massaua, Red Sea. 



Mexican distribution: Pacific Baja Calif. — Howell 892, from 

 20 fms., Bahia de San Lucas, Aug. 



This species which was originally described from sterile specimens, 

 but in the type material Weber van Bosse found and figured a male 

 nemathecium. The Mexican specimens agree structurally with the 

 original description and with Weber van Bosse's reanalysis of the species. 

 It resembles Mexican specimens of P. rubra var. orientalis, but has 

 distinctly oblique or ascending perithallus cell rows unlike that plant, 

 and is more firmly attached to the substrate by the cementing function 

 of the calcification of the under surface. It differs from P. pacifica by 

 its thinner, but larger-celled thallus, by its larger carpospores and tetra- 

 sporangia, more elevated tetrasporangial nemathecia, and thick, non- 

 clavate paraphyses. 



Peyssonelia mexicana sp. nov. 

 Plate 11, figs. 1-2 



Thallo stricte adhaerenti, 2-3 cm. vel plus lato, maius calcificato in 

 duabus partibus inferioribus, rhizoidibus unicellularibus, 250-550 /* 

 crasso; seriebus cellularum perithalli ascendentibus, cellulis summis 6-8 

 /A diametro maximo; nematheciis tetrasporangialibus elevatis, 130-150 fx 

 crassis; paraphysibus tenuibus, baud ramificatis, circa 7 cellularum; 

 tetrasporangiis 60-100 /t longis, 22-30 /* latis. 



Thalli saxicolous, crustose, firmly and closely adherent to the sub- 

 stratum, rather heavily calcified in the lower %, forming expansions of 

 2-3 cm. or more, attached by short, unicellular rhizoids; 250-550 (600) 

 IX thick, the surface relatively smooth but reflecting the irregularities of 

 the substrate; hypothallus distinct, of regular parallel rows of cells 8-15 

 by 25-30 /* as seen in inferior surface view, about 25-30 jx high, with a 

 thick basal cuticle to 10 /a thick; perithallus of regular ascending, then 



