NO. 2 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 279 



The plant identified by Taylor (1945) as Prionitis kinoensis 

 from the Galapagos Archipelago has been reexamined. It is tetrasporic 

 and agrees with this species in structure and in habit. The tetrasporangia, 

 however, are not confined to the apices, but occur in segments well re- 

 moved from the ends. 



Zanardinula abbreviata (Setchell & Gardner) J. DeToni 

 PI. 19, fig. 64; pi. 20, figs. 65-66 



J. De Toni 1936, n.p. Prionitis abbreviata Setchell and Gardner 

 1924, p. 785, pi. 25, fig. 29, pi. 50b; Dawson 1944, p. 283. Prionitis 

 guaymasensis Dawson 1944, p. 283, pi. 66, figs. 1-2. Zanardinula guay- 

 masensis (Dawson) Dawson 1945b, p. 93; Dawson 1949, p. 234, 238, 

 243. 



Some thirty collections, many of them fertile, have now been as- 

 sembled from the Gulf of California and represent this species in a 

 remarkable variety of sizes and growth forms. The range of variability 

 in form is extreme, as shown by the illustrations presented here (figs. 

 64-66) and those cited above. Intergrades, however, are present which 

 appear to link all of these together. Despite this recognition of unity 

 among them, it seems advantageous to the student and collector of these 

 Gulf of California plants, and as an aid to identification by means of 

 keys, to designate the major peaks of variability by name. The type of 

 Prionitis abbreviata, as illustrated by Setchell and Gardner 1924, pi. 

 50b, represents the broad, spatulate, dominantly dichotomous form, while 

 the type specimens of P. guaymasensis, as illustrated by Dawson 1944, 

 pi. 66, fig. 1, represent the narrow form with abundant, long-pinnate 

 secondary branchlets. The former may be called Zanardinula abbreviata 

 var. abbreviata and the latter Z. abbreviata var. guaymasensis (Dawson) 

 comb. nov. 



This variable species may be described as follows : Thalli usually 6-8 

 cm. high, forming rather loose, irregular clumps consisting of one to 

 several much-branched, flattened fronds with segments 1-3 mm. wide, 

 from a discoid holdfast, dark brownish or blackish in color, cartilaginous 

 when dry; primary branching mostly dichotomous, the intervals irregu- 

 lar; secondary branching pinnate, mostly distichous, sometimes in part 

 polystichous in age, the branches scattered and few, to abundant and at 

 intervals of 1 mm. or less, short, determinate and peg-like, or to 1-1.5 

 cm. long and blade-like, sometimes indeterminate and provided in turn 

 with pinnae; segments of variable width in different plants, 1-3 (4) mm. 

 broad; ultimate segments in some plants spatulate and rather blunt, in 



