291 
middle of the ray. Length, 36-38 “; diameter with rays, 68-72 
#; without, 16-18 “; isthmus, 12 ». 
Type in Herb. Johnson, 276. Bridgeport, Conn. 
A single specimen was found having five rays on one end of 
the semi-cell. All the others were typical. 
BoTraNICAL LABORATORY, UNIVERSITY OF MICHIGAN. 
Explanation of Plate 211. 
(Reduced one-fourth in photographing.) 
a, front view of cell; b, vertical view; c, side view. 
‘ the Xanthidium antilopasum (Breb.) Kutz., var. Minneapoliense Wolle, forma. 
500. 
2, Staurastrum leptocladum Nordst. ><560. 
3: 6 “ var. cornutum Wille. 560, 
4. St. gyrans n. sp. 770, 
5. Cosmarium cyclicum Lund. <5 60. 
6. C. impressulum Elfv. 770. 
7- C. subglobosum Nordst. 770. 
8. Euastrum binale Ralfs. var. insulare Wittr. 779. 
9. St. bicoronatum n. sp. XII50. 
10. St. irregulare West. 1150. 
11. C, sulcatum Nordst. x 560. 
12. C. nudiceps n. sp. X< 560. 
13. C. calcareum Wittr. 770. 
14. C. angulare n. sp. 770. 
15. Onychonema leve var. micracanthum Nordst. ><770. 
16. St. elegantissimum n. sp. ><560. 
17. C. tessellatum (Delp.) Nordst. >< 560. 
Recent Discoveries of Cycadean Trunks in the Potomac 
Formation of Maryland. 
By Lester F. WARD. 
Scarcely any fact is better known to paleontologists than that 
Of the discovery ‘by Philip T. Tyson, in 1859, of two large 
‘ycadean trunks and some other fragments in the iron ore region 
of Maryland. These were not described at the time, and were 
only briefly mentioned in his first report as State Agricultural 
Chemist, published in January, 1860 (p. 42), where he refers to = 
