140 ERBSII-WATER AhGJE OP THE UNITED STATES. 



frond punctate; f. v. segments turgid on the surface, at the middle without circular inflations; 

 tr. V. ellii)tic, witli a single largo inflation at each side ; c. v. end lobe entire at the margin, 

 its divisions circular. (A.) 



Remarhs. — I have seen only a very few specimens in a gathering made in Saco 

 I>akc, New Hampshire, by Dr. Lewis, which difter considerably from the typical 

 form in the proportion of the breadth and length. There are also certainly four, 

 if not more, umbonations on the face of each half-cell. These are nowhere dis- 

 tinctly spoken of as existing, and Mr. Archer states there are none visible in the 

 front view of E. ansatum. They are, however, represented in the side view of the 

 original figure, and are said to be very noticeable by Mr. Archer himself, when 

 the desmid is so looked at. In the Saco Lake specimens they are always seen in 

 the front view with great difficulty, and in some cases I failed entirely to demon-' 

 strate them, so that they do not aftbrd a good character for the indication of a new 

 species. 



Fig. 1, pi. 13, represents a front view of a Saco specimen, magnified 450 dia- 

 meters. 



G. Lobi polares non-evidenter discreti. 

 C. End lobes not evidenthj distinct. 

 E. ele^ans, (Breb.) Ktz. 



E. minus, oblonguni, dianietro dujtlo longins, utroque polo bifidum, segnientis introrsnm rotun- 

 datis; scmicellulis sursum modice attenuatis, utroque margine laterali bi- vel tri- siuuatis, 

 sinu superiori vel intermedio profundiori, sub polo utrinquo dente acute prominente ; eytio- 

 dermate subtiliter punctato, punctis irregulariter sparsis ; zygosporis globosis aculeatis, 

 aculeis elongato-sulmlatis. (11.) 



Long. 0.001 2"._0.002". Lat. max. circiter 0.001 1". (R.) 



Syn. — E. elegans, (Brebisson,) Ktjtzino. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 

 185. 



Sab. — South Carolina; Georgia; Florida; Rhode Island ; Bailey. White Mountains, (F. W. 

 Lewi.s). 



Frond minute, scarcely twice as long as broad, oblong; segments with their basal portion emar- 

 ginate at the sides, connected by a broad neck with the terminal portion ; ends protuberant, 

 rounded, acutely emarginate at the centre, pouting; s. v. with an inflation at the base of the 

 segments, sides concave, ends rounded. Sporangium orbicular, spinous. (A.) 



Remarks. — According to Prof Rabenhorst E. rostratum, Ralfs, whicli is noted 

 as an American species by Bailey, is a variety of E. elerjans. Its peculiarities, ac- 

 cording to Rabenhorst, are as follows : " Forma magis evoluta, profundior sinuata, 

 segmentis polaribus latioribus, angulis acutis, dente paulo longiore." 



Fig. U, pi. 21, represents the outline of the frond as viewed laterally; fig. 2, 

 pi. 13, a front view of the frond, magnified 750 diameters. 



E. biiiale, (Turpin) Ralfs. 



]•]. niiiiinunn, dianietro paulo vel suljduplo longius, in sect, transversa oblongo-cylindricnm, 

 medio tuniidum, utroque polo roluudatum ; semicellulis indistincte trilobis, lobis basalibus 



