FRESH-WATER AJjQJE OF THE UNITKD STATES. 



123 



Eemarks.— The only specimens tliat I have seen of this species were found in a 

 spring in the Phihxdelphia City Park, near Columbia bridge, 

 lig- 11' pl- 12, was drawn from one of these specimens. 



Genus SPH^ROZOSMA, Corda. 



Celluloe compressas, medio transversim profunde incisie, itaque bilobatjB, in quoque lobo massa 

 clilorophyllosa quadriradiata iiufleum amylaceura involvcnte prteditaj, in filum planum tseuiiformum 

 literaliter isthmis conjunct*. ZjgospoiiB globosse vel ovules, glabras. (R.) 



Syn. — Isthmoxira, Ktz. 



Odontellee, spec, Ehrb. 

 Idhmiae, spec, Men EG. 

 Spondylosium, Bkeb. 



Cells compressed, transversely very deeply incised in the centre and therefore bilobate, furnished 

 in each lobe with a quadriradiate mass of cliloropbyl surrounding a starch grain, conjoined laterally 

 by isthmuses in a tasniform fascia. 



Remarhs. — I have never found any species of this genus in America. Professor 

 Bailey has, however, detected the following: — 



Spli. excaTatiiui, Rat-fs. 



Sjth. plerumque nudum (sine tubo nnieo.so) sph. vertebratnm nnilto minus ; cellulis diametro 

 duplo-longioribus, medio e.xcavato-constrictis, a latere ellipticis utroque polo rotundatis; lobis 

 brevibus truncato-rotundatis, Ifevibus vel granulato-denticulatis ; isthmis biuis parvis verru- 

 eiformibus; zygosporis pleruraque ovatis. (R ) 



Lata, filer. 0.00047"— 00032". (R.) 



Syn. — Sph. excavaium, Ralfs, British Desraids, p. fiT. 



Eah. — Florida; Georgia; South Carolina ; Rliode Island ; Bailey. 



"Joints longer than broad, having a deep sinus on both sides and two sessile glands at each 

 margin at their junction, very minute, seldom more than twenty-five joints in the filament, 

 which is fragile, and finally separates into single joints ; at their junction, in the front view 

 are two minute glands or processes, situated one near each angle, and nearly invisible before 

 the escape of the endochrome. The joints are nearly twice as long as broad and much con- 

 stricted in the middle ; the constriction is like an excavation or broad sinus on each side, so 

 that the margins of the filaments appear sinuated. The endochrome is pale bluish-green 

 with minute scattered granules. The transverse view is oblong with four .Sessile glands, two 

 on each side and situated near the ends." — Ralfs' Brit. Dcsm., p G7. 



Sph. piilchi'iim, Bailey. 



Sph. cellulis oblongo-quadrangularibus, diametro duplo-brevioribus, acute incisis, arete con- 

 nexis; lobis oblongis rectis, apice rotundatis; isthmis nullis, vagina mucosa ampla dis- 

 ncta. (R.) 



Syn. — S. pulchrum, Bailey. Ralfs, British Desmid., p. 209 (Cum icone). 



Eab. — West Point, New Tork ; Princeton, New Jersey ; Bailey. 



" Joints twice as broad as long, deeply incised on each side ; junction margins straight, con- 

 nected by short bauds." 



RemarJc.- — " Prof. Bailey informs me that this species is twice as large as Sph. 

 vertebratum" Ralfs. 



