148 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



Several collections occur, especially from Guaymas, Sonora, in which 

 the branches are longer, more attenuate and more nearly cylindrical 

 than in the usual examples of this plant. In these respects they agree 

 with Taylor's Nayarit specimen. 



In connection with the Nayarit specimen just mentioned, some re- 

 marks may be made regarding the identity of Amphiroa compressa var. 

 tenuis Taylor. This variety was neither illustrated nor adequately de- 

 scribed. The holotype material, Taylor 39-642b, came from the same 

 dredge-haul as specimens identified by Taylor as A. franciscana, A. di- 

 morpha, A. foliacea, and A. peninsularis and seems best recognized as a 

 variant of the latter (Taylor 39-642a). A paratype from near Manta, 

 Ecuador (Schmitt 403-35) shows considerable similarity to some por- 

 tions of the A. peninsularis specimen under Taylor 39-642a, and, since 

 A. peninsularis is also known from Ecuador may best be considered a 

 variant of that species, which is synonymous with A. zonata. In any 

 event there seems insufficient reason either for accepting A. compressa 

 var tenuis as a distinct entity or for referring it to A. compressa. 



Amphiroa crosslandii Lemoine 



Lemoine, 1929, p. 50, pi. 4, fig. 3, text fig. 13; Taylor, 1945, p. 191. 



Thalli to 1 cm. high, forming a low spreading tuft consisting of 

 several erect segments from the basal crust, each branching rather dense- 

 ly and irregularly dichotomously or trichotomously in 1 plane, the 

 branches tending to be depressed and to spread horizontally; segments 

 compressed to flattened throughout, simple or forked, 350-500 /jl in dia- 

 meter, but forked segments or those giving rise to a fork much expanded 

 at the fork or distally, to 1.0-1.2 mm. wide, commonly 1.5-2.0 mm. long, 

 the ultimate segments usually with expanded, rounded apices ; zonate 

 bands rather prominent; cortex thin, medulla tending to show an alter- 

 nation of about 3 tiers of long cells with one of short cells ; genicula in- 

 conspicuous, more or less concealed by calcification, usually not coinci- 

 dent with forkings, of 3-4 tiers of medullary cells surrounded by a thin, 

 persistent cortical layer; tetrasporic conceptacles numerous, prominent, 

 domoid, scattered over the segments, 250-400 /x in diameter. 



Type: Holotype is a specimen from the St. George Expedition of 

 1923-24 in the herbarium of the Museum National d'Histoire Naturelle, 

 Paris. An isotype preparation is on slide 1500 in HAHF. 



Type locality: At a depth of 27 meters off Isla Gorgona, Pacific 

 Panama. 



