THE GREEN ALGAE OF NORTH AMERICA 379 



25, PI. I, figs. 9 and 13. Slender, stipe 1^-3 cm. high, with 

 occasional spindle-shaped swellings; disk cup-shaped, 6-7 p. 

 diam. ; rays 25-30, not strongly united, the blunt margin with a 

 broad, deep, squarish depression ; corona superior about 90 n 

 diam., with 2 or 3, sometimes 4 hair-scars on each ray ; aplano- 

 spores about 160 /u. diam., about 80 in a sporangium; gametes 

 developed before the release of the aplanospores from the 

 sporangium. St. Thomas, Jamaica. 



Indian and South Pacific Oceans. 



In general appearance like a delicate A. crenulata, but with 

 only one disk, different shape in the margin of the disk, usually 

 more hair-scars than in A. crenulata, and with rays less firmly 

 united. 



3. A. FARI.OWII Solms, 1895, p. 27, PI. Ill, fig. i ; P. B.-A., 

 No. 1032; Acetabulum Farlowii Howe, 19053^.577. Stipe 1-2 

 cm. high; disk 4-7 mm. diam., nearly flat; rays 20-30, lightly 

 coherent or free, slightly compressed towards the obtuse or 

 truncate ends ; corona superior .15 mm. diam., with two hair- 

 scars on each ray ; aplanospores 40-120 in a sporangium. Fla. 



Distinguished from A. crenulata by the loosely attached or 

 entirely free rays, and from A. caliadus by the flattish disk with 

 obtuse rays; in mature plants the rays are often entangled, so 

 that the regular form of the disk is lost. 



4. A. POLYPHYSOIDES Crouan in Schramm and Maze, 1866, 

 p. 101 ; Solms, 1895, P- 2 9> P1 - IV, figs. 2 and 6; Vickers, 

 1908, p. 28, PI. XLVII ; Acetabulum polyphysoides Howe, 1909, 

 p. 92, PL VI, figs. 16-20; PI. VII, figs. 5-9. Stipe seldom over 

 i cm. high, disk single, cup-shaped or nearly flat, 2-5 mm. 

 diam. ; rays 11-25, mostly 12-18, vesicular, from obovoid to sub- 

 fusiform, obtuse and rounded at the end, loosely united -by a 

 thin calcification; corona superior 75-150/1 diam., a whorl of 

 5-13, usually 8 or 9, hair-scars on each ray ; aplanospores 90- 

 190 p. diam., 6-50 in a sporangium. W. I. 



The few and swollen rays sufficiently distinguish this species 

 from the preceding, apart from the characters of the hair-scars. 



Forma deltoidea (Howe) nov. comb.; Acctabnlum polyphys- 

 oides dcltoideum Howe, 1909, p. 92, PI. VI, fig. 21 ; PI. VII, 

 fig. 10. Rays usually 7, much inflated, inversely deltoid or 

 obovoid-deltoid ; hairs scars 6-8. Bahamas. 



Very distinct in appearance by the few and broad rays, but 

 there are intermediate forms between this and the typical form. 



5. A. pusilla (Howe) nov. comb.; Acetabulum pusillum 



