314 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3 



Genus PLATYTHAMNION J. Agardh 



Platythamnion tepocensis sp. nov. 



Plate 72, Fig. 1 



Frondes usque ad 3 cm. altae, axi primaria conspicua raagni-cellulari, laxe 

 ramosa provisae; ramulis lateralibus plerumque 500 [i longis, oppositis, superne 

 curvatis, acute attenuatis, ramulis secondariis 30-110 ii longis, nonnullis suppressis; 

 cellulis glandularibus frequentibus; cellulis axium primariarum superne 50-70 ji 

 diam., inferne usque ad 150 (A aut plus diam., 1-1.5-plo longioribus. 



Attachment organs unknown; plants to 3 cm. high, with a sparingly 

 branched, conspicuous, large-celled main axis bearing well-developed 

 lateral ramuli and reduced ramuli on upper and lower sides of axis cells, 

 producing a complanate general aspect to the fronds ; lateral ramuli aver- 

 aging 500 fi long, opposite, curving upward and tapering to a sharp point, 

 bearing opposite, acute secondary ramuli 30-100 u long, some of these 

 commonly suppressed, occasionally with tertiary ramuli ; gland cells fre- 

 quent, principally on primary and secondary ramuli ; main axis cells 

 cylindrical, 50-70 fx diam. above, to 150-]- fi below, 1-1.5 times as long 

 as wide; antheridial clusters mostly at the base and at the lower nodes 

 of the primary ramuli ; tetraspores and cystocarps unknown. 



Type: D. 379, dredged in 22 meters, Tepoca Bay, Feb. 4, 1940. 

 Herb. AHF no. 54. 



From the nature of the branching — bearing four sets of branches 

 on each axis cell, two well-developed lateral sets and two reduced sets, 

 dorsal and ventral — this plant is seen to fall into the genus Platytham- 

 nion J. Ag. The Gulf specimens correspond to none of the previously de- 

 scribed species from the American coasts, all of which have been figured 

 byKylin (1925). 



Genus GRIFFITHSIA C. Agardh 

 GriflFithsia pacifica Kylin 



Kylin, 1925, p. 58, figs. 38, 39. 



From a comparison of our material with specimens of Grifflthsia 

 pacifica from the coast of California we are quite certain that the Gulf 

 material is referable to this species. Most of the author's specimens are 

 somewhat more slender and less strongly articulated than the typical 

 Californian plants, but D. 382 is an example which fulfills perfectly all 

 dimensional requirements. 



D. 43, 73, shallow water at low tide, Guaymas Harbor, Jan.; D. 163, 

 rock shingle in lower littoral, south side of Tiburon Island, Jan.; D. 

 382, dredged in 22 meters, Tepoca Bay, Feb. 



