158 
Transactions of the Society. 
Long. 13*5-14*5 /x ; lat. 15-16 u; lat. isthm. 3*8- 
5*5 fji. 
Hah. Devil’s Jumps, Frenskam Common, Surrey. 
One example was noticed with a gelatinous investment 39 /x in 
diameter. 
28. S. Bieneanum Rabh. (Alg. No. 1410; St. orhiculare b. 
Bieneanum Rabh. Flor. Europ. Alg., iii. p. 200). PI. III. 
fig. 27. 
Zygosporse globosae, spinis validis integris plerumque 
leviter curvatis ad basem dilatatis obsessae. 
Diam. zygosp. sine spin. 32-35 /x, cum spin. 50-52 /x ; 
long. spin. 8-10 yix. 
Hah. Near Goring, S.E. Oxfordshire, with zygospores in 
abundance. 
This species, although described by Rabenliorst, was afterwards 
placed by him as a variety of St. orhiculare (Ehrnb.) Ralfs. It 
certainly does not belong to the latter species, but is a very character- 
istic and constant species throughout the British Isles. The semi- 
cells are more convex on their lower margins than on their upper 
ones, and the latter are always truncate or slightly retuse in the 
middle. This inequality of curvature causes a slight outward 
divergence of the semicells ; the angles of both the front and vertical 
views are acutely rounded, and the membrane is always delicately 
punctate. Moreover, the zygospore differs from that of St. orhiculare 
in the spines being shorter, stouter, and fewer. We figure a zygo- 
spore of St. orhiculare from Maine, U.S.A. for comparison (PI. III. 
fig. 28). 
29. S. suborbiculare sp. n. PI. IY. fig. 48. 
A S. orbiculari differt apicibus semicellularum truncatis et 
leviter retusis, membrana dense et subtiliter punctulata, zygo- 
sporis spinis brevissimis multe inflatis ad basem ornatis. 
Long. 35-44 /x ; lat. 35-37 ya ; lat. isthm. 7 * 5-9 * 5 ya. 
Hah. Glas Maol, Perthshire, Scotland. 
Messrs. Roy and Bisset, in their ‘ Scottish Desmidiese,’ pi. iv. fig. 7, 
figure a zygospore of “ St. orhiculare ( forma ?).” From the form of 
the cells and zygospore it does not belong to that species. We have 
seen this in abundance from Glas Maol, and give it the above name. 
30. S. Kjelmanni Wille (Ferskv. Alg. fr. Nov. Semi., p. 50, 
tab. xiii. figs. 50-3). 
Yar. rotundatum var. n. PI. IY. fig. 46. 
Yar. psene duplo-longior quam latior; semicellulis sub- 
rotundatis, granulis irregulariter ordinatis. 
Long. 43 /x ; lat. 25-26 * 5 ya ; lat. isth. 13*5 ya. 
Hah. Ogden Clough, W. Yorks. 
Some algologists place St. Kjelmanni Wille as a variety of 
