knowlton.] TERTIARY PLANTS OF NORTH AMERICA.. 229 
Thuja sp., Dn, Trans. Roy. Soc. Canada, vol. v, sec. iv, p. 34, 1887. 
[Fossil wood.] 
Canadian upper Laramie: Four hundred mile Point, forty-ninth 
parallel; Middle Fork Old Man River. 
Thuja sp., Dn. Trans. Roy. Soc. Canada, vol. v, sec. iv, p. 33, 1887. 
[Wood.] 
Belly River series: Old Man River; Ribstone Creek; Twenty-Mile 
Creek. 
Thuja sp., Kn. Bull. Geol. Soc. Am., vol. viii, p. 134, 1897. 
Fort Union group: Lightning- Creek, Converse County, Wyoming. 
THYRSOPTERIS Kunze. Linmea, vol. ix, p. 507, 1834. 
Thyrsopteris alata Font. Potomac Fl., p. 124, pi. xxxvi, f. 3, 1889. 
Potomac formation: Near Potomac Run, Virginia. 
Thyrsopteris angustifolia Font. Potomac Fl., p. 131, pi. xliv, f. 4; 
xlv, f. 3; xlviii, f. 2; xlix, f. 3, 4; lv, f. 2; lviii, f. 8, 1889. 
Potomac formation : Trents Reach, near Dutch Gap Canal, near 
Brooke, and near Potomac Run, Virginia. 
Thyrsopteris angustiloba Font. Potomac Fl., p. 134, pi. xlviii, f. 3-5 ; 
lv, f. 3, 1889. 
Potomac formation: Fredericksburg, near Dutch Gap Canal, 
Trents Reach, and White House Bluff, Virginia. 
Thyrsopteris bella Font. Potomac FL, p. 139, pi. liii, f. 5; lv, f. 6, 7; 
lvi, f. 2, 5; lvii, f. 1, 5; lviii, f. 4, 1889. 
Potomac formation : Fredericksburg, Trents Reach, White House 
Bluff, and near Dutch Gap Canal, Virginia. 
Thyrsopteris brevifolia Font. Potomac FL, p. 121, pi. xxiv, f. 5, 10. 
Potomac formation: Dutch Gap Canal, Virginia. 
Kootanie: Great Falls, Montana. 
Thyrsopteris brevipennis Font. Potomac PI., p. 124, pi. xxxiv, f. 3; 
xxxvi, f. 2; xxxvii, f. 3, 9; xxxviii, f. 1; xli, f. 4, 1889. 
Potomac formation: Dutch Gap Canal and Deep Bottom, Vir- 
ginia; Baltimore, Maryland. 
Kootanie: Great Falls, Montana. 
Thyrsopteris crassinervis Font. Potomac FL, p. 130, pi. xli, f. 1-3, 
1889. 
Potomac formation : Fredericksburg, Virginia. 
Thyrsopteris crenata Font. Potomac Fl., p. 127, pi. xxxix, f. 1, 2, 
1889. 
Potomac formation : Fredericksburg, Virginia. 
Thyrsopteris decurrens Font. Potomac FL, p. 130, pi. xliii, f. 7; 
xlvi, f. 2, 4; xlix, f. 5-7, 1889. 
Potomac formation : Dutch Gap Canal, Fredericksburg, near 
Brooke, near Potomac Run, Virginia. 
Thyrsopteris densifolia Font. Potomac FL, p. 129, pi. xxxix, f. 3; 
xl, f. 2-5; li, f. 5, 1889. 
Potomac formation : Fredericksburg, and near Brooke, Virginia. 
