Howe : Phycological studies 495 



a species, and it appears that the eaiHest available name for it that 

 conforms with prevailing rules of nomenclature is Ilalimcda 

 discoidea Decaisne,* under which name the species is described 

 below : 



Halimeda discoidea Decaisne, Ann. Sci. Nat. II. i8 : 102. 

 1842. 



7 Ha/itncda papyracea Zdir\2ird.'\ ¥\or3i 34: t^j. 1851; Mem. R. 



1st. Ven. 7: 288. //. ij. f. 2. 1858. 



Of a light bright-green color and lubricous when living, becom- 

 ing yellowish- or albescent-green and more or less pergameneous 

 or papyraceous and smooth to the touch on drying, suberect or 

 decumbent, 5-15 cm. in height or length, subsessile, very lightly 

 calcified, the calcification usually confined to the narrow area l>'ing 

 between the coherent ends of the peripheral utricles and the distal 

 ends of the subcortical utricles, in the oldest parts sometimes in- 

 volving the distal half of the subcortex ; the branching in one 

 plane, mostly frequent or somewhat congested, usually di- or tri- 

 chotomous, the larger subbasal segments sometimes originating 

 five or six branches : segments discoid, enervate, deltoid-obovate, 

 semiorbicular, reniform, or subelliptical (with longer axis trans- 

 verse), 6-35 mm. broad, mostly 0.3-1.2 mm. thick, those near 

 base scarcely different, but sometimes attaining thickness of 1.75 

 mm., margins entire, the surfaces commonly nitent when dry or in 

 younger parts dull and very minutely spongiose : peripheral utri- 

 cles mostly hexagonal in surface view, 40-85 n in diameter, often 

 fusing in twos, threes, or rarely fours, and therefore appearing 



* The name. Cora Hina discoidea 'Es^tr (Pflanzenthiere, Fortsetz. 2, Cotallina, pi. 

 II. 179S-1806) appears to have fallen short of effective publication according to both 

 the Vienna and the Philadelphia codes of nomenclature, so may be ignored in deter- 

 mining the correct name of the present species, whether Esper had this species before 

 him or not. The name first appeared on a plate, illustrating a large Halimeda of the 

 Tuna group, without analysis of parts and without descriptive or explanatory text. In 

 a continuation of Esper's work by F. L. Hammer, many years later (3 : 356. 1830), 

 the name (changed to "discoTdes") is found in the synonymy of Halimeda Tuna, 

 with a reference to the plate. Esper's plant cannot be satisfactorily determined without 

 examining the original, which, it would seem, is not now to be found in his collections 

 preserved at Erlangen. Lamourou.x is sometimes quoted as having a Halinuda dis- 

 coidea but it would appear that he never actually published such a binomial. In 1812, 

 in establishing the genus Halimeda, I>amouroux mentions among the examples Coral- 

 Una '■'■discoidea Esper," but we do not find that he ever actually printed or adopted 

 the name Halimeda discoidea. In the same paper he mentions " Corallina Jlabellum 

 Ell." as an example of his new genus Udotea, but when four years later he came really 

 to enter the species into Udotea it became Udotea Jlabellata instead of Udotea Flabellum. 



f See footnote on following page. 



