114 DESMIDS OF THE UNITED STATES. 



very broad, cuneate, end convex, or slightly sinuate on the 

 margin ; lateral lobelets nearly entire. 



Diameter 75-85 //.. 



This species is met with only occasionally, Pennsylvania, 

 New Jersey, Florida. 



M. TRUNCATA, (Corda.) Kails. Plate XX XVI II, figs. 6-9. 



Orbicular; semicells five lobed ; lateral Lobes shallow ; end 

 lobe very broad, truncate, angles bidentate; lateral ones 

 ineised-dentate. 



Diameter 50-100 jjl. 



One of the most common species of this genus. Variable 

 in size and in the structure of the margins ; sometimes the 

 lobelets are obscurely toothed ; again very distinctly notched, 

 and another form is frequent with the angles drawn out into 

 loug spinedike points, fig. 7. The truncate ends are usually 

 mure or less rounded ; tig. 8 is a peculiar form with the ends 

 perfectly Hat, and not detached from one another after multi- 

 plication by division. 



M . oonferta, Lund. [M. gramdata, Wood). Plate LIII, fig. 12. 

 Broad-elliptic, central sinus deep, narrow linear; semicells 

 five lobed, Lobes and Lobules always close; polar lobe sub- 

 cuneate, more or Less widened from the base to the end, sides 

 concave and apes convex but roundly emarginate in the 

 middle, angles furnished with two or three small papillae; 

 lateral Lobes nearly equal, bisected, and again divided, each 

 lobule with apex furnished with two papilla-like points. 



Var. BAMATA, Wolle. Plate KXXVIII, figs. 3, 4. 



In this variety, the polar lobe is not oomferta, compact, close 

 against the adjoining lobes, as in the true form, but widely 

 separated in the whole length ; the open space is produced by 

 the contraction of the lobe below the apex, thus giving it a 

 hamate form. 



Diameter 88100 //., length slightly more. 



Ponds, Mt. Everett, Mass. 



The only locality from which I received the typical form 

 is Aiken, S. C, the same from which Wood had it. This 

 species was first known in Sweden, and described by Cleve, as 

 M. crenata. Lundell separated it from that species and 



