902 MR W. WEST AND MR G. S. WEST ON 
specimens they are relatively obtuse. They may be horizontally disposed, but are 
more often shghtly turned upwards. The isthmus is very shortly cylindrical. 
The species can be compared with St. Clepsydra, Nordst. (and its var. acuminatum), 
but the differences are very considerable, especially in the vertical view. 
21. St. brevispinum, Bréb. 
Var. obversum, var. n. (Pl. 7, fig. 15). 
Var. cellulis latioribus quam longis ; semicellulis obverse semiellipticis cum mucrone 
prominentiori ad angulum superiorem unumquemque, sinu angustiorl apicem ampliatum 
versus, dorso semicellularum leviter convexis, ventro multe ‘convexis ; a vertice visis 
cum mucronibus prominentioribus. 
Long. 38-42; lat. 45-49°5 w; lat. isthm. 10°5-11 #. 
Hab.—Loch Fadaghoda, Lewis, Outer Hebrides. 
Var. altum, var. n. (Pl. 7, fig. 16). 
Var cellulis longioribus quam latis ; semicellulis multe altioribus, dorso valde con- 
vexo; a vertica visis lateribus minus concavis, angulis crassioribus, mucronibus 
minutis. 
Long. 57-66 «; lat. 483-50); lat. isthm, 12°5-15°3 «. 
ffab.—Lochs nan Cuinne and Ruar, Sutherland (J. Murray)! Lochs Fadaghoda, 
an Sgath, and an Tomain, Lewis ; and Loch Diracleet, Harris, Outer Hebrides. 
These two varieties differ from one another considerably, but are undoubtedly forms 
of St. brevispinum. 
22. St. subtricum, Borge, in Bihang. till K. Sv. Vet.-Akad. Handl., Bd. 17, No. 2, 
HOO pee te Utd. 
Long. 17-18 » ; lat. 17-21 4; lat. isthm. 7°5-8°5 uw ; crass. 8—9 u (Pl. 7, fig. 20). 
Hab.—Loch Fadaghoda, Lewis, Outer Hebrides. 
We have recorded a triangular form of this species from the south of England (vide 
Journ. Roy. Micr. Soc., 1896, p. 157, t. 4, f. 39), but the typical form has not been 
observed before from the British Islands. 
23. St. sublevispnum, W. & G. S. West, in Journ. Linn. Soc., bot., xxxiil., 1898, 
p. 314, t. 18, £ 20-22. 
Long. 33 «; lat. 46; lat. isthm. 8°5 u. 
f1ab.—Loch Fadaghoda, Lewis, Outer Hebrides. 
The specimens were slightly larger than the American ones, but otherwise precisely 
similar. The “body” of the Staurastrum is very small, and the processes are 
cylindrical, except for their obtusely attenuated apices. The specimen figured (PI. 7, 
fig. 23) shows the first stage of cell-division, the elongation of the isthmus. 
24. St. subnudibrachiatum, sp. n. (Pl. 7, figs. 18, 19). 
St. mediocre, circiter 1}-plo latius quam longum (cum processibus), leviter con- 
strictum, sinu latissime aperto; semicellule suborbiculares, marginibus lateralibus 
in processus glabros longos rectos leviter subdivergentes productis, apicibus processuum 
