68 ON THE GENERA ANADYOMENE AND MICRODICTYON. 
not able to examine either the species discovered by Botta in the Red Sea 
or the one found in the Canaries, as there are no specimens of them in 
the British Museum or my own collection, which only contains the 
species discovered in Natal by Dr. Krauss, and the three species col- 
lected by Professor Harvey in Australia and the Tongan Islands. 
The four specimens in the British Museum appear to be very dis- 
tinct species, but it is very difficult to distinguish them in words; this 
difficulty partly arises from the very imperfect state in which they are,— 
a defect generally incidental to Chlorospermous A/g@ in a dried state, 
and especially to 4/gce of such a tender and fragile nature as the genus 
under consideration. 
In the following schedule I commence with the three species named 
by Decaisne, of which I know nothing except what is contained in 
the works quoted. 
* Frond umbilicate, affixed by the centre. 
1. M. Velleyanum ; frond expanded, fan-shaped, fixed in the centre ; 
filaments very minute, slender; cells longer than broad; the colour 
blackish when dry, sombre green when fresh.—C. umbilicata, Velley, 
Linn. Soc. v. 169. t. 7. (1799). Hydrodictyon wmbilicatum, Agardh, 
Syst. 83. M. Velleyanum, Decaisne, Arch. du Mus. ii. 117 (1834); 
Ann. Soc. Nat. ser. 2, xvii. 327 ; Endlicher, Mantissa, ii. 1843. 
Agardhianum, Decaisne ; Harvey, Algæ Austral. Exsiccate, n. 568. 
Has. Australia: New South Wales, on the stem of a large fucus, 
Governor Hunter, Velley ; Harvey, * Phycologia Australica,’ t. 50. 
Sandwich Islands, Gaudichaud; abundant in Port Jackson and Para- 
matta River, Harvey. 
Decaisne established this species from Colonel Velley's figures and 
descriptions, and from a fragment that M. Gaudichaud brought from 
the Sandwich Islands, which is in the herbarium of the Jardin des 
Plantes at Paris. 
2. M. Calodictyon ; filaments moderately thick.—** Fronde solitaria, 
suborbiculari e viridi fusco nigrescente, cribrosa, margine dissecta 
lobataque ; venis quinis, mediis erectis, binis inferioribus patentibus 
iem deflexis) membrana nulla annexis. Discus mamillatus scutatus, 
bine digs unbes mw solitaria,  planiuscula, diame tro 
m pee pellucidis, confervoides, primariis quinis, quorum tres medians 
4 
