MICRASTERIAS. 119 



polar lobe broadly cuneate, end truncate-sinuate, angles 

 cuspidate. 

 Diameter of cell 180 ^. 



Mt. Everett, Mass. 



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

 ber of lobules and their greater similarity of form. 



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



XLIII, fig. 1. 



Cells orbicular, smooth ; semi-cells rather indistinctly five 

 lobed ; lobes dichotoniously divided ; ultimate subdivisions, 

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

 cuneate, emarginate, and its angles dentate. 

 Diameter 150-200 /<. 



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 Win. IS". Hastings near Rochester, New 

 Hampshire. 



Diameter variable, 190-250 //. 



M. SPECIOSA, Wolle. Plate XLV, tigs. 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 niucros 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. 



