FRESH-WATER ALG^ OP THE UNITED STATES. 145 



country, but I have never met with it. All the specimens which have come under 

 my notice were obtained in "Shepherd's Dam," near Greenwich, Cumberland 

 Counfy, New Jersey. None of them were as large as the maximum of the European 

 measurements of which Rabenhorst gives 0.0109" as the diameter. 



Fig. 5, pi. 13, represents a frond of this species, magnified 260 diameters. 



m. denticnlata, Be£:b. ? 



M. permagna, paulo longior quam lata, laevis; semicellulis quinqnelobis (psene 9 lobis) ; lobis 

 intermediis et basalibus simillimis, bilobatis, lobulis item in lobulis bifidis duobns divisis ; 

 lobo polare angusto, cuneato, in apice plus minus inciso ; margine minute denticulate. 



Diam.—La.t. .0092". Long. .011." 



Syn. — M. denticulata, Brebisson. Ralfs, British Desmidieae, p. 70, et Aecher, Pritchakd's 

 Infusoria. 

 M. denticulata, Brebisson. ? Rabenhorst, Flora Europ. Algarum, Sect. III. p. 192. 



Sab. — Pennsylvania; Wood. Florida; Bailey. 



Yery large, a little longer than broad, smooth ; semicells with five lobes (scarcely 9) ; basal 

 and intermediate lobes alike bilobate, lobules also divided into two bifid lobules; end lobe 

 narrow, wedge-shaped, more or less incised at its apex ; margin minutely denticulate. 



Remarhs. — Prof. Rabenhorst gives M. denticulata, Breb. as merely a variety of 

 M. furcata^ Ag., stating that it only difi'ers from the latter in the marginal incisions 

 and teeth. Not having access to the original description of Brebisson I cannot 

 express an opinion as to whether Prof B,. is correct or not, but the specimen from 

 which the above description was drawn up (and which is figured on plate 13) cer- 

 tainly differs from M. furcata very essentially in the arrangement of its lobes, and 

 is, I feel confident, M. denticulata, Breb. of Ralfs and Archer. 



Fig. 6, pi. 13, is a drawing of this plant, as seen by myself, magnified 260 

 diameters. 



M. radiosa, Aa. 



M. maxima, orbicularis, laevis, antecedenti simillima, diifert inprimis segmentis ultimis tumidis 

 in apicem bi- tri- fidum attennatis, lobo polari vix prominnlo, apice sinuato, ad ntrumque 

 angalum bi- tri- dentato. (R.) Species mihiignota. 



Diam— 0.0016". (R.) 



Syn. — M. radiosa, Agardh. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 192. 



ffab. — Florida; Bailey. 



Frond orbicular, smooth ; segments 5-lobed ; basal lobes twice, middle lobes generally thrice 

 dichotoraous, ultimate subdivisions inflated, attenuate towards the end, bidentate; end lobes 

 emarginate, its angles dentate. (A.) 



M. fimbriata, Ralfs. 



M. magna, orbicularis, laevis (nonnunquara superficie aculeis singulis sparsis); semicellulis 

 quinquelobis, lobis omnibus confertis, basalibus angustioribus, repetito bilobulatis, lobis inter- 

 mediis duplo latioribus, repetito-bilobulatis, lacinulis extremis leviter emarginatis, in angulis 

 spinis elongatis armatis; lobo polari prominulo, in apice obtuse sinuato- vel- undulato- emar- 

 ginato, angulis lateralibus rotundatis, ad marginem superiorem spinis singulis vel geminis 

 obsito (rarius nudo). (R.) Species mihi ignota. 



19 August, 1872. 



