1908] Cushman,— New England Species of Micrasterias 109 
polar lobe widely separated from the lateral ones, which are scarcely 
separated from one another by a shallow open sinus, each lobe once 
divided, the lobules obliquely truncated and denticulate; surface of 
the cell with scattered denticulate granules, most numerous towards 
the ends of the lobes, and an irregular group centrally above the 
isthmus on each semicell Length 124-158 м, breadth 105-138 y, 
polar lobe 50-75 y, isthmus 18-28 и. Me.: Orono (Harvey). N. H.: 
North Woodstock! Mass.: Amherst (W. West); Lake Quinsigamond 
Worcester (Stone); Stony Brook, Weston! Misery Island, off Beverly 
Farms! Medford! Plainville! Pondville! Carver’s Pond, Bridge- 
water! Swansea! Framingham (H. C. no. 726)! К. I: Near 
Providence (Bailey). This species seems to be common in material 
from southern New England but has been met with very seldom in 
collections north of Massachusetts. Like other species of this genus 
itis variable. The polar lobe assumes various forms yet none of them 
with the exception of the following variety is united with other distinc- 
tive characters. The four large granules at the apex of the terminal 
lobe seem to be lacking more often than they are present and the whole 
cell is often nearly smooth. 
17a. MICRASTERIAS AMERICANA, var. RECTA Wolle, Bull. Torrey 
Club, 1876, p. 122; 1881, pl. 6, fig. 2; Desm. U. S., 1884, p. 112, 
pl. 32, fig. 3: W. & G. 5. West, Brit. Desm., 1905, p. 119, pl. 54, 
fig. 4. Extremities of the processes of the polar lobe all very short 
and rounded, apex of the polar lobe nearly straight, sinuses separating 
the lateral lobes and lobules reduced and a much more even outline 
developed than in the type. Length 143 м, breadth 121 4, polar lobe 
65 u, isthmus 28 и. N. H.: North Woodstock! Mass.: Carver's 
Pond, Bridgewater! Framingham (H. C. mo. 703)! Pond near 
Old North Cemetery, Nantucket! There are varying gradations 
between this variety and the type from which it is difficult to group but 
as a rule the variety seems to be distinct. It is much less common in 
New England than the typical form. 
18. MICRASTERIAS RINGENS Bailey, var. sERRULATA Wolle, Bull. 
Torrey Club, 1885, p. 128, pl. 51, fig. 15; Fr. Alg., 1887, p. 41, pl. 59, 
fig. 15; W. &. С. 5. West, Some Desm. U. 5., 1898, p. 296. Length 
156 м, breadth 152 и. N.H.: Laconia (H.J. no. 650, 679). Whether 
this is the same as M. mahabuleshwarensis Hobson or not seems to be 
an open question. Upon examining Johnson's slides nos. 650 and 
679 I was unable to find the specimens in condition for critical exami-- 
