Messrs. Sullivant and Wormley on the Strie@ of Diatoms. 253 
—P. Wormleyi, 52.*—P. obtusatum, 56.+—P. Sciotoensis, 40.t— 
Synedra radians, var.? a common fresh water species in this yi- 
cinity, has on the hoop about 75 strize in the 001”, very diffi- 
cult, when balsam mounted, to resolve, owing probably to their 
shallowness—Grammatophora subtilissima, 70 to 75 on t 
001"; and at the circumference about 75 in 001”, More or 
less of these lines from. the margin of the umbilicus, i a 
“ere 
which they are resolved near the former point. The umbilicus 
mail is rayed, and in certain portions of the light exhibits curved 
es 
To those interested in. these matters it may not be unaccepta- 
ble to:state the means and method by which the above measure: 
m ordinary eye-piecing. The value of the Jackson 
micrometer (a scale of ‘008") with each of the objectives was 
* Pinte ; : bilities 9 fish 
wa Wi , Sulliv.—Lanceolatum, conspicue sigmoideum, in apices 
acutos subito ieetinatinn sicher “008”: striis trans. et long. 52 in ‘001’. 
Fresh water; Columbus, Ohio, Prof. T. G Wormley ; Genessee river, N. Y., Mr. 
rath bles P.g cerii, but is a smaller species, more evidently sigmoid and with 
abruptly attenuated ends: its strise are more difficult to , being shal- 
texture of the y. i 
. 
* 
Fresh Sensim attenuatum ; long. ‘005’ ; striis trans. fry to 40 in -001’", 
water; Columbus, Ohio: Genessee river, N. Y., Mr. 0. A. : 
less acute 
