Atlantic. Tangier, Rübenl — Canaries, D'Orbignyl, Hb. Mus. Paris; type of//, platydisca 

 Decne. — St. Vincent, Cape de Verde, Challenger\ Welwitsch\, Iter Angolense, n°. 247. — 

 Antilies, Herb. Shuttleworth\ n°. 298. — "Carolina, Bermudas or Caribees", Clerkl, in Herb. 

 Sloane vol. 318. fol. 48. — Barbadoes, Herb. Dickiel — Walsingham, Bermuda, Farlow ! — 

 Guadeloupe, Mazel, n°. 74, ser. I n os . 33, 148'»*, 390, 3790. — Jamaica, Sloane ! Herb. Sloane 

 vol. I. fol. 2. — Key West, Harveyl Hooper\, Alg. exsicc. Am. Bor. Farlow, Anderson 

 and Eaton n". 41. C. Messinal, Phycotheca Bor.-Amer. Collins, Holden and Setchell, n". 

 167. — Jupiter Inlet, Curtiss\, Algae Floridanae ser. I. — ■ Sisal, Yucatan, Schottl n°. 786. — 

 Barra Grande, Challenger ! — Nicoga, Central America, Herb. Berkeley in Herb. Kew. ! — 



INDIC. Mauritius, de Robillard\ — Rodriguez, I. B. Balfour ! ■ — Zanzibar, Stuhlmann !, I. n". 



I205 a . — Dar es Salaam, Holst !, n". 1264 pro parte. — Aden, Ferguson\, n". 444. — 

 Ceylon, Harveyl, n". 70. Ferguson\, n°. 67. — Singapore, Beccari\, sub nom. H. papyracea 

 Zan. — Endeh, Flores, Weber van Bossel, n°. 11 10. — Maumeri, Flores, Weber van Bossel 

 n". 1032. — Pare-Pare, Celebes, Weber van Bosse. — de Bril], Weber van Bossel 

 Siboga-Expedition. Labuan-Badjo ! — Key dula, reef! — Tual, reef! — Elat, Great Kei Island, 

 reef! - Buka Bay ! — Rotti, reef! — Sumba, Nangamessi ! — Eau! — Kabala dua ! — 

 Sarasa, Postillon Islands ! — 



Pacific. Parry Shoal, Arafura Sea, Bassett Snüth ! — Macclesfield Bank, China Sea, Bassett 

 Smithl — Funafuti, David\ in Herb. Mus. Brit. n"\ A. 21 pro parte, A. 58. B. 10, 11 and 

 12. — Ovalau, Fiji Islands, Graeffel, in Herb. Gruhow. — Fiji Islands, Herb. Mus. Brit\ - 

 Mangaia, Gill\ — Upolu, Herb. Mus. Brit\ — Friendly Islands, Home ! Harveyl, n°. 21 pro 

 parte. — Minerva Reef, " Herald" ! — Tongatabu, Graeffel Challenger \ — Borabora, 

 Society Islands, Bory de St. Vincent \, in Herb. Mus. Paris sub nom. H. Lessonii. — Sandwich 

 Islands, Hot/iel — Victorian Bank, M" Donaldl 54I292. — Payta, Peru, Sinclair ! — 

 Kamtschatka, a Voyage de la Venus" !, in Herb. Mus. Paris sub nom. U H. discoided' '. — - 



Plants varying in length to about 20 cm., generally much less ; slightly incrusted with 

 lime, branching in one plane. Root short, more or less bulbous. Lowest joint more or less 

 thick, cylindrical or cuneate, often deeply calcified ; thickening sometimes extends to several 

 joints above the root. Other joints slightly calcified, varying in form from flat and discoid to 

 elongate-cuneate, not ribbed, margin entire ; varying in size to 35 mm. long, 22 mm. broad, 

 averaging 1 mm. thick J ). The small joints are as a rule much thicker than the large ones, 

 the largest being ver)- thin. 



Filaments of central strand fuse in twos and threes at the apex of each joint, the fused 

 filaments varying in length, branching later di-or trichotomously. Filaments as a \vhole not connected 

 at the point of fusion. 



Peripheral cells as a rule regularly hexagonal in surface view ; 40 p. to 75 >j. across, 

 75 ij. to 100 u, long; sum of length and breadth fairly constant. Side walls of adjacent cells 

 in contact for V20 — 1 /io of their length. 



forma typica. 



H. Titna Lam. 

 Upper joints small, sometimes rather thick; reniform, discoid, or transversely oblong (fig. 1). 



1) The numbers given in relation to external characters refer only to the extvemes which have come under my notice. 1 have, 

 of course, no desire to constrain the species within these limits. 



