NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 23 



and frequent, semi-erect, indeterminate axes 6-10 mm high; primary 

 axes 55-65 /x in diameter, bearing paired, opposite distichous branches, 

 (sometimes with an additional third branch), and a determinate branch 

 always opposite an indeterminate branch; paired determinate branches 

 spiraling, not distichous; cells in main axis 3-4 times as long as broad; 

 determinate lateral branches mostly 200-300 /x long, somewhat attenu- 

 ated, usually incurved, the terminal cells blunt to acute, simple or 1-3 

 times forked beginning with the 3rd cell, the cells 10-15 [x in diameter, 

 1.5-2 diameters long, but the basalmost shorter; gland cells frequent, 

 scattered, much smaller than the single bearing cell; gominoblast 

 consisting of a 3 or 4-lobed cluster 240 /x long, from the basal cell 

 of a determinate lateral; spermatia on short (12-15 /x) spermatangia; 

 tetrasporangia 1 or 2, adaxial, sessile, on the 1st or 2nd cell of a 

 determinate lateral. 



Type: J. T. Howell 613, Aug. 4, 1932, in Herb. California 

 Academy of Sciences (236524). 



Type locality: Epiphytic, at a depth of 37 m., San Jose del 

 Cabo, Baja Calif., Mexico. 



Mexican distribution: Gulf of Calif. — D. 6983, Bahia Salinas, 

 Isla Carmen, 4-30 m.; D. 6906, 6914, 6934, Canal de San Lorenzo, 

 Isla Espiritu Santo, 8-20 m.; D. 6731, 6744, Punta Frailes, 8-16 m.; 

 Howell 646a, 721, San Jose del Cabo, 40 m. 



It is evident from an examination of these specimens and those 

 of A. breviramosus Dawson that the two species are closely related. The 

 latter have determinate branches regularly in whorls of three while 

 the former are predominately pinnate. However, several of the specimens 

 of A. sublittorale show an occasional 3rd branch at a node. In size, 

 habit and other vegetative characters, they are similar. Fertile material 

 has been found in most of the collections of A. sublittorale, but none has 

 appeared in the more numerous collections of A. breviramosus. The 

 latter is known from a number of intertidal or shallow water collections, 

 while all A. sublittorale materials are from sublittoral habitats. 



Crouania attenuata (C. Ag.) J. Ag. 



PI. 7, fig. 4 



J. Agardh 1842, p. 83; Dawson 1957a, p. 7; Dawson 1952, p. 431; Setchell & 



Gardner 1930, p. 167. Mesogloia attenuata C. Agardh 1824, p. 51. Batracho- 



spermum attenuatum Bonnemaison, (nom. nud.) in C. Agardh 1824, p. 51. 



Thalli epiphytic or saxicolous, little-branched or tufted, 1-3 (5) cm. 

 high, attached by rhizoids, the main thallus parts cylindrical and 

 somewhat terminally attenuated, ± mucilaginous, consisting of a cylin- 

 drical, axial, non-corticated cell row about 200 jx in diameter near the 

 base, more slender above, of cells 1-3 (4) diameters long, each giving 

 rise near the distal end to a whorl of usually 4 compound determinate 



