MICRASTEEIAS. 119 



polar lobe broadly cuneate, end truncate-sinuate, angles 

 cuspidate. 



Diameter of cell 180 /j. 

 Mt. Everett, Mass. 



Separated from M. Torreyi, by its smaller size, the less num- 

 ber of lobules and their greater similarity of form. 



M. EADIOSA, (Ag.), Ealfs. Plate XXXV, figs. 1, 2, 3; Plate 

 XLIII, fig. 1. 

 Cells orbicular, smooth ; semi-cells rather indistinctly five 

 lobed ; lobes dichotomously divided ; ultimate subdivisions, 

 inflated, attenuated, furcate at the ends. End lobe narrow 

 cuneate, emarginate, and its angles dentate. 

 Diameter 150-200 pL. 



A beautiful species and not rare, easily recognized by its 

 many and deep incisions ; it is variable in size and number of 

 subdivisions ; the latter range from twenty to forty in a semi- 

 cell. 



Var. PUNCTATA, West., J. E. M. S., Nov., 1888. Plate XLIII. 



fig. 1. 



This differs from the usual forms of M. radiosa in having a 



distinctly punctate cytioderm with the division of the lobes 



more like those of If. papillifera, especially the ultimate ones. 



Pond, Massachusetts. 



M. SwAiNEi, Hast. Plate XLII, fig. 1. 



A form very near M. radiosa, differing mainly in the usually 

 more or less elongated lower lobe of the basal division of the 

 semi-cell, which is a constant feature; frequent in large 

 gatherings made by Wm. K". Hastings near Eotehester, New 

 Hampshire. 



Diameter variable, 190-250 j^. 



M. SPEciosA, Wolle. Plate XLV, figs. 1, 2. 



Small, somewhat longer than broad, five lobed ; lateral 

 lobes unequal, the basal pair usually with only half as many 

 divisions as the intermediate ones ; each basal lobe consist- 

 ing of one, and the intermediate of two lobulets, the angles 

 of each section drawn out into two spine-like points ; ter- 

 minal lobe rather narrow, linear, the end exserted and much 

 dilated, usually with three prominent mucros at each angle; 

 center an obtuse angled notch, standing free with a rather 

 wide gap between it and the adjoining lobes ; a series of 

 small spines often observed on the margins of the lobes. 



