295 
Apex of semi-cell sometimes shows three slight elevations corre- 
sponding to the three lobes. 
ST. PROTRACTUM nov. nom. (.S¢. grallatorium forma Wolle") 
(428). This is certainly not a form of St. grallatorium. WVolle 
gives no note on it, but merely figures it. It may be described as 
follows: Length slightly less than breadth. Sinus shallow, linear, 
gaping widely in the outer half. Semicells nearly square with 
basal angles rounded and armed with two minute spines. Sides 
nearly parallel. Near the apex each is produced into a stout ser- 
rate ray tipped with three spines. Apex of semi-cell truncate, 
projecting above the rays and bearing several serrations. End 
view triangular, sides concave, angles drawn out into rays. Sur- 
face marked by several rows of serrations. Around the centre of 
the semi-cell (in end view) six larger bifid or trifid projections. 
Diam.=50-52 p; length=44 ». Whitmore Lake, Mich. Fig. 35. 
* St. leve Ralfs. (450). Whitmore Lake, Mich. Frequent. 
Diam.—14y; length=18y. Fig. 34. 
De Toni cites among the localities for this species “ Americae 
borealis (Wolle),"” but I cannot find that Wolle ever reported it, 
and believe this must be a mistake. 
* St. Reinschit Roy (348). Duval county, Fla. This does not 
agree exactly with Roy’s description, but it comes so near it that 
I place it here provisionally, The spines are short but distinct. 
It is smallerthan the type. Diam.—24,; length—20p. Fig. 15 
* Xanthidium antilopaeum Kiitz. forma _Javanicum Nordst. (324). 
Ann Arbor, Mich. Diam.—52p; length=52 4; thick.— 30 p; isth. 
=1I2y. The position and number of spines on the end of the 
semi-cell is variable, even in the same individual, but they show a 
tendency to arrangement in a single series. Fig. Io. 
X. concinnum Arch. var. Boldtianum West. (422). (Arthrodes- 
mus hexagonus forma Boldt.) Duval county, Fla. Occasional. 
Very minute. Diam.—12y; length—14y; thick—6y; isth.— 
4y. Nearly like Boldt.’s Fig. 17, but with sharper angles. In 
front view this looks like an Arthrodesmus, but in vertical view it 
10 Wolle, F. Desmids of the United States. 7.57. f 20.27. 1892. : 
"De Toni, J. B. Sylloge Chlorophycearum omnium hvcusque cognitarum. 
1227. 1889. 2 
12 Boldt, R. Bidrag till Kannedomen om Sibiriens Chlorophyllophyceer. Ofvers. 
K. Vet. Akad. Forh. 1885: 109. 74 5. 7.77. 1885. 
