j 
~I 
SCOTTISH FRESHWATER PLANKTON, 54 
26. STAURASTRUM CONSPICUUM, sp. n. (PI. 14. fig. 4.) 
S. permagnum, circiter 1{-plo latius quam longum, profun- 
dissime constrictum, sinu lineari sed aperto, ad extremo sub- 
amplhiato, extrorsum valdeaperto; semicellule elliptico-fusiformes, 
ventre valde convexo, dorso convexo et late truncato ad medium, 
angulis valde mamillatis et incrassatis ; a vertice vise triangu- 
lares, lateribus late concavis, angulis acute rotundatis et mamil- 
latis; membrana delicate scrobiculata. 
Long. 83-108 p ; lat. 111-134 p; lat. isthm. 21-27 p. 
Hab. Loch Shin, Sutherland. 
This plant is one of the largest and most striking species of 
the genus Staurastrum, and, considering its size, it is somewhat 
surprising that it has so long escaped observation. It was 
searce in the plankton of Loch Shin, but occurred abundantly at 
Rhiconich in a small pool amongst rocks, along with Plewro- 
tenium nodosum, Staurastrum sexangulare, S. verticillatum, and 
other rare Desmids. It can be compared with S. majusculwm, 
Wolle, from which it is easily distinguished by the form of its 
semicells, its sinus, and the form of the vertical view. 
27.8. GRANDE, Buln. in Hedwigia (1861), p. 51, t. 9. f. 14. 
Long. 88-98 »; lat. 88-111 p; Jat. isthm. 21-24 p. 
Hab. Loch Shin, Sutherland. Loch Nan Eun, Outer Hebrides. 
Loch Doon, Ayrshire: 
This species was present in moderate quantity in the plankton 
of the above-mentioned lakes. It was subject to certain varia- 
tions of form, some of the individuals being proportionately 
wider than others, aud many were noticed with a less convex 
back as in the form mentioned by Lundell (in Nov. Act. R. Soc. 
Scient. Upsala, ser. 3, viii. (1871) no. 2, p. 72, t. 4. f. 11). 
28. &. PsEUDOPELAGICUM, sp. n. (PI. 18. figs. 1-3.) 
S. submediocre, circiter 13-plo latius quam longum (cum 
processibus), profunde constrictum, sinu aperto et acuminato : 
semicellule obverse subsemicirculares, apicibus leviter convexis, 
angulis in processus breves validos divergentes productis, apicibus 
processuum profundissime bifurcatis; corpore et processibus 
granulatis, granulis in annulis concentricis circa processus, a 
vertice vise triangulares, lateribus levissime concavis vel convexis, 
angulis in processus breves robustos productis. 
Long. sine proc. 27-345 p, cum proc. 57-71 4; lat. sine 
proce. cire. 23-30 pn, cum proc. 63-86°5 p»; lat. isthm. 7°5-13 pu. 
fab. Loch Shin, Sutherland. Loch Tay, Perthshire. 
