NO. 1 TAYLOR : PACIFIC MARINE ALGAE 171 



KEY TO GENERA 



1. Thallus not articulated 2 



1. Plants with the erect portions flexibly jointed 6 



2. Plants larger, crustose, lamellate or branched, but not flexibly 

 jointed 3 



2. Plants minute, epiphytic, the conceptacles not surrounded by an 

 evident vegetative crust Choreonema 



3. Crusts small, very thin and fragile, sometimes lightly calcified 4 



3. Crusts thicker, either firmly attached to hard substrata or them- 

 selves rather massive ; often w^ith branched protuberances . 5 



4. Tetrasporangial conceptacles discharging by several pores Melobesia 



4. Tetrasporangial conceptacles discharging by a single pore Fosliella 



5. Tetrasporangial conceptacles discharging through several pores 

 Lithothamnium 



5. Tetrasporangial conceptacles discharging through a single pore 

 Lithophyllum 



6. Fronds with conceptacles all lateral, often numerous, scattered 

 over the segments 7 



6. Fronds with terminal conceptacles, at least in part ... 9 



7. Medullary filaments in the segments and in the flexible joints one 

 cell long in each instance Lithothrix 



7. Medullary filaments in each segment several cells long . . 8 



8. Medullaiy filaments in the segments of alternating long and 

 short cells Amphiroa 



8. Medullary filaments in the segments of cells of uniform length 

 Bossea 



9. Branching dichotomous Jania 



9. Branching at least in part pinnate 10 



10. Fronds with both terminal and lateral conceptacles . . Joculator 

 10. Fronds with terminal conceptacles only Corallina 



ARGHAEOLITHOTHAMNIUM Rothpletz, 1891ioi 



Archaeolithothamnlum Crosslandi Lemoine 



Lemoine 1929, p. 57, pi. 2, figs. 1, 2. 



Reported from I. Isabela, Archipielago de Colon. 



101 With this entry and with similar ones following other genera of coralline 

 algae, the writer introduces those records of Galapagos Islands calcareous marine 

 algae which Lemoine published in 1929 on the basis of collections made by Cyril 

 Crossland during the Saint George Expedition in 1924. 



