29 



bus, medio processibus similibus tribus radiatis ordinatis. Diam. 



.0015 "-200 . 



Coll. by Rev. H. D. Kitchel in Gilder Pond, Mt. Marcy, Vt. 



Ralf's Sf, spiuosiim bears a similarity, but is separated by having 

 two or more spines on each side beside the one terminating each 

 angle. St. furcatiun^ Ehrb., is also akin, but has more spines. These 

 forms are moreover, granularly roughened, not smooth. The spines 

 are ftot properly "lateral " but central, the ends projecting over the 

 sid.es. 



Siaurastrum proboscidium^ Breb., var. Americanum, n. var, 

 (Plate XIII, Fig. 10.) This plant was collected in Crystal Bay, St; 

 Lawrence River, Canada, by J. M. Adams. It bears some simil- 

 arity to a variety of St, asperum, described bv Brebisson, and also to 

 a form, Javaiiica^ described by Nordstedt ; but it differs in the ar- 

 rangement of the granules and in the shape of the rays (proboscidii), 

 which are longer and. more cylindrical. 



Staurastrum TRiDENTiFERUM, //. sp. (Plate XIII, Fig. 13.) St. 

 exiguum leve, sinu amplissimo; semicellulis ellipticis, dorso convexo, 

 vel subplano, angulis in aculeos tres rectos divaricatos productis, 

 a vertice visis triangulanbus, lateribus modice retusis, tribus aculeis 

 in angulos impositis. Diam. sine aculeis .0008" ; cum ac, .001". 

 Hab. in a pond near Bethlehem, Pa. 



This plant is nearest a form of St. dejectum, but is separated by 



the three spines at the angles. 



XANTHIDIUM, Ehrb. — Xanthidium tetracentrotum, n, sp, 

 (Plate xiii, Figs, 14 and 14', front and end view. X. parvum, cir- 

 citer tarn latum quam longum, leve, constrictione acute cuneata (non 

 lineari) ; semicellulis subreniformibus" vel subhexagonalibus,^ basi 

 subplana, dorso late rotundo-truncato, uno angulo mediano utrinque 

 in aculeos geminatos breves acutos producto ; tuberculo centrali 

 minus elevato; cytiodermate levi vel serie singula parvularum 



tr n 



granularum oraedito. Diam., sine sp. .0013 -0015 ; cum sp., 

 .0024 -.0025 ; long. .0015 -.0010 . 



Hab. Ponds, Sussex Co., New Jersey. 



The shape of the semicells is very near that of X, fasciculatum, 

 but they are much smaller and bear only two pairs of aculei, not four 

 or six. 



BATRACHOSPERMUM, Roth.— ^. vagum, Roth., van Raven- 

 EUi, n. var. B. bi-tri-polices longum, crassum flavo-aerugineum, sine 

 corticulo, vel rarius ramlilis accessoriis; articulis diametro (ad.oo6''.) 

 plerumque aequalibus vel paulo plus minus, acbrois;^ramis primariis 

 parcis ; ramulis verticilli plerumque brevibus ; verticiUis confertissi- 

 mis, nonnumquam nuUis, sed saepius quoque geniculo cum 2-3 



fasciculis brevissimis instructo. 



Collected by H. W. Ravenel, at St. John's, Berkley, S. C. 



This is a distinct form, particularly in the absence of the acces- 

 sory filaments which constitute the corticular covering or rind of the 

 primary filaments. Bory is credited with a variety of like character, 

 but of dark purple color, verticils far apart and branchlets long; 

 mine on the contrary is of yellowish green or light aeruginous color, 

 verticils very close and branchlets very short. The articulations or 



