FRESH-WATER ALG^ OF THE UNITED STATES. 157 



Hab. — America ; Ehrenberg. 



Frond in front view broader than long ; constriction deep, acute not linear ; segments subellip- 

 tic, sometimes irregular spines subulate, geminate, marginal, central protuberance cylindrical, 

 truncate border minutely dentate. L. (not including spines) 5^^". B. ^j^^" to ^^/'. 



X. cristatnm, Br£b. 



X. parvnm, Iseve ; semicellulis subhaemispherico-reniformibus, utroque polo aculeo unico in- 

 curve, ambitu aculeis octo geminatis, a dorso ovato-ellipticis, utroque polo aculeis ternis, in 

 medio plerumque aculeo abbreviato. (R.J Species mihi ignota. 



Z>iam.— -0.00196". R. 



Syn. — X cristatum, Br£bisson. Ralfs, British Desmidiess, et Rabenhokst, Flora Europ. 

 Algarum, Sect. III. p. 224. 



JTab. — South Carolina ; Georgia ; Florida ; Bailey. 



Frond rather longer than broad ; constriction deep, linear ; segments subreniform or truncate 

 at ends ; spines straight or curved, subulate, marginal, one at each side,' at the base of the 

 segment, solitary, the others geminate, in four pairs ; central protuberance short, conical. (A.) 



X. coronatum, Ehrb. 



X. semicellulis subglobosis binis, aculeatis, ubique asperis, aculeis crassis apice truncatis triden- 

 tato-coronatis quatuor utrinque dorsalibus, uno utrinque latere medio. (R.) Species mihi 

 ignota. 



Syn. — X. coronatum, Ehrenberg, Terbreitung, p. 138, et Rabenhorst, Flora Europ. Alga- 

 rum, Sect. III. p. 224. 

 Asteroxanthium coronatum, KtJTZiNG. Rabenhorst, {loc. cit.) 



nab. — ^America ; Ehrenberg. 



Bemarh. — Mr. Archer appears to think that this species is simply a form of 

 Staurastrum furcigerum. (Beeb.) ; see Pritchard's Infusoria, p. 743. 



X. fosciculatum, Ehrb. 



X. parvum, singulum, constrictione profunda linear! ; cytiodermate Isevi vel sublaevi ; semicel- 

 lulis oblongo-reniformibus vel hexagonis, diametro duplo longioribus, ambitu aculeis gracilibus 

 geminatis 4-6, a dorso ellipticis, utroque polo aculeis quatuor instructis. (R.) Species mihi 

 ignota. 



Zliawi.— 0.00228"— 0.00256". (R.) 



Syn. — X/ascicwZo^Mm, Ehrenberg. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 223. 



Sab. — South Carolina ; Georgia ; Florida ; Rhode Island ; Bailey. 



Frond about as long as broad; constriction deep, linear; segments somewhat reniform or sub- 

 hexagonal, twice as broad as long, spines slender, subulate geminate, marginal, in four or six 

 pairs; central protuberance short, conical, somewhat truncate. (A.) 



Genus AETHRODESMUS, Ehrb. 



Cellulse profunda constrictse ; semicellulaB compressse aut oblongae, utroque polo aculeo subulato 

 firmo instructae, aut quadrangulares, angulis in aculeum rectum vel curvum productis, a dorso vel 

 ellipticse vel fusiformes. Massa chlorophyllacea in fascias quatuor radiantes disposita. (R.) 



Cells profoundly constricted ; semicells compressed or oblong, furnished at each end with a subu- 

 late spine, or else quadrangular with the angles produced into straight or curved spines, the dorsal 

 aspect, elliptic or fusiform. Chlorophyl masses disposed in four radiating fascia. 



