JURASSIC FLORA OF DOUGLAS COUNTY, OREG. 



141 



54. Williamsonia ? sp. Font. Bracts of 



Williamsonia Nos. 2, a, b, c. 



55. Ginkgo digitata (Brongn.) Heer. 



56. Ginkgo Hiittoni (Sternb.) Heer. 



57. Ginkgo Huttoni magnifolia Font. n. 



var. 



58. Ginkgo lepida Heer. 



59. Ginkgo sibirica Heer. 



60. Ginkgo sp. Font. Aberrant Gink- 



gos. 



61. Phoenicopsis ? sp. Font. 



62. Taxites zamioides (Leek.) Sew. 



63. Brachyphyllum mamillare Brongn. 



64. Araucarites ? sp. Font, (cone scale). 



65. Pinus Nordenskioldi Heer. 



66. Cyclopitys oregonensis Font. n. sp. 



67. Sphenolepidium oregonense Font, n, 



sp. 



68. Samaropsis ? oregonensis Font. n. 



sp. 



69. Male ament of conifer. 



70. Yuccites hettangensis Sap.? 



71. Undetermined leaf, No. 1. 



72. Undetermined leaf, No. 2. 



73. Carpolithus olallensis Ward n. sp. 



74. Carpolithus Bucklandii Willn. ? 



75. Carpolithus oregonensis Font. n. sp. 



76. Carpolithus elongatus Font. n. sp. 



77. Carpolithus douglasensis Font. n. sp. 



In determining from these plants the age of the strata that contain 

 them, 40 must be eliminated as of no value. There are 22 new species, 

 2 new varieties, 7 species not positively determined, and 9 forms not 

 specifically determined. It may be said of these that none are incom- 

 patible with the conclusion that the age of the strata is Jurassic, On 

 the contrary, so far as they throw any light on the question of age, they 

 indicate that it is Jurassic. The species that were doubtfully determined 

 are the only ones that have any bearing on the question. They have at 

 least some affinity with forms known from estabhshed geological horizons. 



The plant doubtfully determined as Adiantites Nympharum has an 

 affinity with Heer's species from the Lower Oolite of Siberia; Pterophyllujn 

 minus comes from the Lower Oolite of Yorkshire; Ctenis auriculata is 

 found only in the Oroville strata, which are probably Lower Oohte in age • 

 Marchantites eredus comes from the Lower Oolite of Yorkshire ■ Yuccites 

 hettangensis is obtained from the Infralias of Hettange, a lower horizon 

 than the Lower Oolite; Carpolithus Bucklandii comes from the Lower 

 Oohte of Yorkshire. Thirty-seven species and varieties, over half of the 

 entire number, are forms found in formations whose age is more or less 

 fully established. 



The following species have beeii found only in the Oroville strata of 

 California: Cladophlebis vaccensis, Tceniopteris orovillensis, Macrotceniop- 

 teris calif ornica, Ctenophyllum angustifolium, Ctenophyllum Wardii, Ctenis 

 orovillensis, Ctenis grandifolia. There are thus 7 species found only in 

 the Oregon and Oi'oville beds. 



