﻿BISPORANGIATE AXES. 1 67 



eating a virtually cosmopolitan range of this unique floral type throughout at least 

 all of the older and middle Mesozoie, as follows : 



1. Cycadeaidea etrusca Cap. & Sohns (22). Not structurally known, although 

 with well-outlined ovulate cone and conserved pollen grains. (Italy.) 



2. C. ingens Ward (187). Ovulate cone and disk of thirteen ouee-pinnate, 

 basally aduate fronds, fully known. This is the species on which the original dis- 

 covery of the bisporangiate strobili may be said to rest. (Piedmont-Black Hawk 

 region, South Dakota.) 



3. C. Jenneyana Ward. Cone and disk of ten or eleven fronds, fairly well 

 known. (Piedmont-Black Hawk region.) 



4. C. dacotensis. Complete structure known from a large number of wonder- 

 fully conserved axes borne on various trunks. Disk fronds once-pinnate, and 

 normally eighteen in number. (Minnekahta, South Dakota.) 



5. C. superba. The number of disk fronds unknown. (Minnekahta, South 

 Dakota.) 



6. C. sp. Disks small, and probably with few fronds. Synangia very large. 

 Observed in specimen figured on page 60. (Minnekahta, South Dakota.) 



7. C. Pay 11c i. Disks small, ovulate cone large and certainly functional. 

 Number of microsporophylls unknown. Species nearest of all American forms to 

 Bcniiettites Gibsoiiianus. (Minnekahta, South Dakota.) 



8. Cycadella ivyomiiigeusis Ward. Known from smallest and youngest 

 bisporangiate strobilus observed ; 1 cm. in diameter. Fronds of the disk thirteen 

 in number, in agreement with the very different cycad Cycadeaidea ingens. Strobili 

 too young to display minuter features. (Freezout Hills, Carbon County, Wyoming.) 



9. Cycadocephalus Sewardi Nathorst. Oldest bisporangiate strobilus known. 

 From Trias of southern Sweden. Originally interpreted as ovulate. [Cf. fig. 1, 

 plate xlv.) Fronds of disk, seventeen or eighteen. 



10. WiUiamsonia gigas. Known inferentially from various disk impressions 

 or casts. Fronds numerous — fifteen or twenty. (Europe, India, and elsewhere.) 



