NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 31 



roae in the Hancock Foundation herbarium but had not been cited in 

 publication. 



Callithamnion marshallense Daws. 

 PL 10, fig. 1-3 

 Dawson 1957, p. 117, fig. 25a-c; Dawson 1960, p. 50. 



Thalli attached to other algae or to shells or debris, loosely tufted, 

 4-5 mm. high, consisting of an irregularly semi-prostrate part attached 

 by modified lateral branchlets with adherent terminal discs, some of the 

 attachment branchlets distinctly catenate in their cell form and unlike 

 vegetative branchlets; main axis 80-90 ft in diam., non-corticated, of cells 

 1.0-1.5 diameters long; lateral branchlets 20-30 /x in diam., lax, long, 

 somewhat attenuate but terminally blunt, mostly simple, curved, 

 alternate on the bearing axis, but not always from every cell, mostly 

 spirally arranged, often with approximately 1/5 divergence, but some- 

 times in part tending to be distichous; tetrasporangia tripartite, sub- 

 spherical, about 40 jx in diam., sessile and adaxial, one or several in 

 the lower half of a lateral branchlet in mid-parts of thallus. 



Type: Dawson 13695, August 21, 1955, in Herb. Bishop Museum, 

 Honolulu. 



Type locality: On shells and dead coral from a depth of 6-10 

 feet in the lagoon, south end of Parry Island, Eniwetok Atoll. 



Mexican distribution: Pacific Baja Calif. — D. 9018 (Hubbs, 

 Johnson and Allanson) Laguna de San Ignacio, 3.25-3.75 m. 



Although sterile, this material, like that from Bahia Uvita, Costa 

 Rica (Dawson 1960) is much like the Eniwetok type. All came from 

 quiet, shallow, sublittoral, bay habitats. 



A strikingly similar plant is D. 2920 from a more exposed intertidal 

 habitat at Punta Santa Rosalia. It has the same structure, branching and 

 dimorphic rhizoidal attachments, but is somewhat coarser and shorter 

 celled throughout. These differences may be due to the more agitated 

 conditions of the environment. 



Callithamnion paschale B0rg. 

 PL 9, fig. 5-6 

 Borgesen 1924, p. 294, fig. 35; Dawson 1959, p. 28, fig. 6b. Callithamnion 

 veleroae Dawson 1944, p. 312, pi. 50, fig. 3-5. 



Thalli tufted, to 2.5 cm. tall, on algal turfs, often growing on 

 articulated corallines, attached by rhizoids; erect parts much branched, 

 the axes to 150 fx in diameter below, ecorticate, or with a few descending 

 filaments, of cells 1.5-2.5 diameters long, alternately branched with 4-5 

 orders, the branchlets ascending, gradually reduced to the ultimate ones 

 15-20 jx in diameter, often somewhat corymbose, of 5-15 cells 1-1.5 

 diameters long, blunt-tipped, the last 2-3 orders of branches usually 

 distichous; lower orders of branches distichous, or in part irregularly 



