COSMARIUM. 97 



C. PYCNOCHONDEUM, N"ord. Plate XXII, figs. 10, 11. 



About one-fifth longer than the diameter; subhexagonal, 

 constriction deep, sinus narrow linear; ends truncate guadri- 

 crenate ; angles inferior and superior obtusely rounded ; 

 sides moderately convex with about six crenae each; at base 

 nine to twelve vertical, or somewhat diverging series of 

 granules ; membranes ornate with additional granules ar- 

 ranged in lines, at the same time radiating and concentric ; 

 the former courses are double, and often triple near the 

 margin; central area within the concentric rows, is nude. 

 Seen from the vertex, or from the side, a basal inflation is 

 evident ; thickness of the cells, equal to about half the 

 length; isthmus measures about half as much as the breadth. 



Diameter 50 //. ; length 79 ju. 



The only locality from which I had this form is Nebraska 

 Notch, Vt., from collections made by C. G. Pringle. It diflers 

 from the typical, Arctic (Spitzbergen) form in its greater pro- 

 portionate length. 



C. PULCHBEEiMUM, ¥ord. Plate LX, figs. 25-27. 



Cells oblong, ends rounded, about one-third part longer 

 than broad, margins crenulate, constriction deep, sinus nar 

 row linear, not ampliated towards the mouth ; semi-cells 

 subsemicircular, inferior angles square, basal center inflated 

 and furnished with about five vertical series of granules ; 

 lateral view broadly ovate, end rounded, and base of each 

 side more or less inflated; membrane granulate near the 

 margins, granules arranged in about four to five concentric 

 series ; area nude between these and the vertical series. 

 Diameter 33 jj.. ; length 10 ^. 



This desmid is proportionately shorter than the typical 

 forms described by Dr. Nordstedt. The one from Brazil and 

 the other from the island of Spitzbergen, which measures one 

 and one-third to nearly twice as long as wide. My specimens 

 are from Minnesota, and from several localities of eastern 

 Pennsylvania. 



C. EADiosuM, Wolle. Plate XXII, figs. 21, 22. 



Cells orbiculate, about one-eighth longer than broad ; semi- 

 cells semicircular, separated by a deep narrow linear sinus ; 

 ends round or slightly depressed, clothed with semiorbicular 

 granules arranged in about thirty-five radiating lines ; basal 

 inflation has about eight vertical, or somewhat diverging 



7 



