NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 113 



The material cited above has been compared with type fragments 

 obtained from the Crouan Herbarium in the Museum of Paris through 

 the kindness of Dr. Pierre Bourelly. They agree in all essential details. 

 The radiating, anastomosing ridges on the thallus surface are particular- 

 ly distinctive and separate it readily from the several Mexican Peys- 

 sonelia species recognized here. 



Corallinaceae Subf. Gorallinoideae 



Key TO THE Mexican Genera 



1. Plants with terminal conceptacles 2 



1. Plants without terminal conceptacles 4 



2. Intergenicular medullary filaments flexuous and interlacing 

 Calliarthron cheilosporioides 



2. Intergenicular medullary filaments straight .... 3 

 3. Branching primarily and dominantly dichotomous . Jania 

 3. Branching primarily and dominantly pinnate . . Corallina 



4. Genicula unizonal 5 



4. Genicula multizonal .... Amphiroa (in part) 

 5. Intergenicular medulla unizonal . . Lithothrix aspergillum 

 5. Intergenicular medulla multizonal 6 



6. Intergenicular medullary cells in transverse zones of long 

 and short cells Amphiroa (in part) 



6. Intergenicular medullary cells in transverse zones of equal 

 length Bossea 



Calliarthron cheilosporioides Manza 



Plate 8, fig. 9 



Manza, 1937, p. 46; Manza, 1940, p. 266, pi. 2; Smith, 1944, p. 

 237, pi. 53, fig. 1. 



Thalli saxicolous, 10-20 cm. high, consisting of several to many 

 erect axes from a crustose basal stratum; erect axes cylindrical at the 

 base, with several intergenicula 1.5-1.8 mm, in diameter and about as 

 long as broad, the intergenicula above first becoming longer, to 2.5 times 

 as long as broad and compressed, then becoming strongly flattened and 

 winged above and with a prominent, thickened midrib; branching 

 generally sparse, in part dichotomous, but mainly irregularly alternate or 

 opposite, distichous; upper intergenicula 4-6 mm. broad and 2.5 mm. 

 long, cuneate to obcordate, the wings acute or blunt; intergenicular 



