232 Rhodora [DEcEMBER 
Cells small, about 2} times as long as wide, with a very slight con- 
striction, very slightly attenuated toward the truncately rounded 
apices, cell wall with delicate longitudinal striations. 
Length 35-40 u; breadth 15.5-16.5 u; isthmus 13.5 p. 
Mass.: Tom Nevers Pond and pond near Old North Cemetery, 
Nantucket! 
PENIUM curTUM Bréb. 
Closterium curtum Bréb., in Desm., 1838, fase. 19, No. 901. 
Cosmarium curtum Ralfs. Brit. Desm., 1848, p. 109, pl. 32, fig. 9. 
Penium curtum Bréb., in Kütz., Spec Alg., 1849, p. 167; W. & G. 
S. West, Brit. Desm., vol. 1, 1904, p. 97, pl. 10, figs. 21, 22. 
Calocylindrus curtus Wolle, Desm. U. S., 1884, p. 54, pl. 12, figs. 
15, 16. 
“Cells small, sometimes minute, a little more than twice longer 
than their diameter, with a distinct median constriction; semi-cells 
attenuated, sides convex, apex rounded and sometimes slightly thick- 
ened; cell wall punctate; chloroplasts with about eight longitudinal 
' ridges." 
Length 22-60 u; breadth 10.5-32.5 u; breadth of isthmus 9.5-30 n. 
Mass.: Amherst (W. West). 
Personally I have not met with this species in New England. It has 
been found in Massachusetts by West and in several states outside of 
New England by Wolle. The description and measurements are 
from the Wests’ British Desmids. 4 
* PENIUM CRUCIFERUM (DeBary) Wittr. 
Cosmarium ? cruciferum DeBary, Conj., 1858, p. 72, pl. 7, G, figs. 
3-6. 
Penium cruciferum Wittr., in Wittr. & Nordst., Alg. Exsiec. No. 
482, 1882; W. & G. S. West, Brit. Desm., vol. 1, 1904, p. 100, pl. 
10, figs. 18, 19. 
Cells small, about 14 times as long as wide, with a slight median 
constriction, apices broadly rounded, cell wall smooth and colorless. 
Length 15.5 x; breadth 10 ji; isthmus 9.3 p. 
Mass.: Lake Watuppa, Fall River, common! 
PENIUM MiNUTUM (Ralfs) Cleve. 
Docidium minutum Ralfs., Brit. Desm., 1848, p. 158, pl. 26, fig. 5; 
Wolle, Desm. U. S., 1884, p. 52, pl. 10, fig. 9, pl. 50, figs. 29-31. 
