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Gen. 4. Euastrüm (Ehrenberg, 1832)Nob. — Euastrum et Cosmarium 
pro max. parte Ralfs, On brit. Desm. 1844; Euastrum et Cosmarium de 
Bary, Conjag. 1858, excl. subsect. Arthrodesmus etsect . Dysphinctium 
et Calocylindrus; Euastrum et Cosmarium Lundell, De Desm. Suec. 
1871, excl. sect. Pleurotœniopsis ; Euastrum Fr. Gay, Mon. loc. Conj. 
1884, excl. sect. Arthrodesmus. — Cell. ellipticæ vel oblongæ,a verlice 
visse ellipticæ, medio transverse (plus minus) constrictæ, sinu lineari. In 
quaque semicell. chromatophorus unus axilis vel (in ingentibus spec.) 
chromatophori bini juxta axin; chromatophori e 4 laminis radiantibus 
compositi, pyrenoidem unicum includentes. Zygosporæ muricatæ vel 
verrucosæ. — Sp. 40. 
Sect. 1. Auteuastrum Nob. — Euastrum Ralfs, de Bary, loc. cit. 
— Cell. symmetrice sinuatæ vel lobatæ, utroque polo sinuato-emarginatæ 
vel inciso-bilobatæ. 
a. In quaque semicell. chromatophorus unicus. 
E. eiegans Kiitz., (3. cebennense nov. var. — Lobi basales bidentati, 
dentibus acutis; lobus polaris sicut apud typum. Long. 30-35, lat. cum 
dent. 18-22, lat. lob.pol. 16-20, isth. 3 g.. 
Hautes Cévennes. 
e. denticiiiatum. — E. amœnum Fr. Gay, Mon. loc. Conj. p. 53, 
non Brébisson. — Cell. parva, paulo longior quam lata, profunde con- 
stricla. Semicell. trilobatæ, lobo pol. sinu profundo, lineari et utroque 
latere duobus dentibus acutis instructo, lobis basalibus tridentatis. Mem- 
brana glabra, in centro granulis 5, juxta marginem granulis 8 ornata. 
Long. 25-28, lat. 18-20, lat. lob. pol. 13, isth. 3^. 
Montagne de la Margeride. 
E. formosum. — Cell. minima, fere tam longa quam lata, profunde 
constricta. Semicell. rectangulares, trilobatæ, lobo pol. cellulæ maximum 
diametrum adæquanti, apice late et profunde sinuato, angulo mucronato 
in utroque latere instructo; lobis basalibus angulatis, vix mucronatis. 
Long. 13, lat. 11, lat. lob. pol. 10, isth. 2 a. 
Hautes Cévennes. 
E. anomaium. — Cell. diametro duplo longior, etiamsupra, rectangu- 
laris, vix profunde constricta. Semicell. rectangulares, diametro longiores, 
vix distincte lobatæ, lobis basalibus vix tumidulis ; lobo polari dilatato, 
rectangulari, medio late sinuato. Membranapunctata, in quoque angulo lobi 
polaris granulo unico instructa. Long. 35, lat. 15, crass. 12, isth. 13 p. 
Rochers suintants sur l’Espinouse (Hautes Cévennes). 
Sect. 2. Cosmarium Nob. — Cosmarii sect . Eucosmarium et Micro- 
