34 FRESH-WATER ALG^E OF THE UNITED STATES. 



C. LAGOENSE, Nord. Plate LX, figs. 26, 27. 



Semi-cell in vertical view, in the middle much swollen 

 and the ends inflated, granules large 5 center smooth. It is 

 an exaggerated development of C. ornatum and hence a 

 variety of it. 



Tewksbury, Massachusetts, and not infrequent in New 

 Jersey ponds. 



C. BIRETUM, Breb. V. Des. II. S. p. 86, var. FLORIDENSE, 



Wolle. Plate LXII, fig. 6 



Differs from the typical form in its somewhat larger size, 

 but principally in the retuse ends. 



Diameter 70 //. 



Frequent along the shores of lake at Kissimme, Florida. 



Genus, TETMEMORUS. V. Des. U. S. p. 90. 



T. GIGANTEUS. Plate LIV, fig. 1. 



Represents a specimen not infrequent with the ends 

 somewhat contracted, differing in this regard from the form 

 Des. U. S. Plate XX. 



Genus, XANTHIDIUM. V. Des. U. S. p. 93. 



X. FASCICULATUM, var. SUBALPINUM, Wolle. Plate LVI, fig. 9. 

 Prof. Delponte, in his DESMIDIACEARUM SUBALPINUM, 

 p. 168, describes this species differently from that described 

 in Des. U. S. p. 93, the variation being mainly in the wider 

 separation of the lateral spines. To distinguish the two I 

 make the above variety. 



Not rare in ponds, New Jersey and Minnesota. 



X. COLUMBIANUM, Wolle. Plate LVI, figs. 10, 11. 



Cells about one-third longer than wide; divided by a deep 

 constriction forming much ampliated, acute-angled sinuses; 

 semi-cells oblong hexagonal, superior and lateral angles each 

 produced into a firm aculeus ; within the margins, four, 

 often indistinct, aculei ; end view more or less regular hex- 

 agonal, each angle somewhat produced and surmounted by 

 a firm aculeus ; within the margin are four aculei, the ends 

 of which often extend over the margin ; cytioderm smooth. 



Diameter 60 JJL ; length 80 //, without aculei. 

 Pond, Ocean County, New Jersey. 



