December 30, 1904.] 



SCIENCE. 



919 



desciiLed embraces nine species, including one 

 fern, tliree cycads and three conifers. The 

 remaining- species belongs to a genus he now 

 calls Ctenopteris and regards it as of uncer- 

 tain systematic position, although, in the pre- 

 ceding part (' Jurassic Flora of Yorkshire,' 

 p. 237) he referred Saporta's Ctenopteris to 

 Ptilozamiies of Nathorst and treated it as be- 

 longing to the Cycadales of doubtful affinity. 

 In this I have followed him for the Jurassic 

 plant P. Leckenbyi, which is common to the 

 Yorkshire flora and that of Oregon. As Sa- 

 porta's name has priority it should stand, pro- 

 vided it is really the same genus as the Ptilo- 

 zamites of Nathorst. 



Both fronds and trunks of recognized cy- 

 cadean plants occur in the Lias of Britain, 

 and Mr. Seward puts both these into what he 

 calls a class, the Cycadophyta. This term he 

 attributes .to JSTathorst, but the latter did not 

 use it in Latin form. I was, perhaps, the 

 first to call attention to the inconsistency of 

 applying the term Cycadales to the foliage of 

 such plants and the term Bennettitales to 

 their trunks, when both kinds are found at 

 practically the same horizon and often in the 

 same beds, with every probability that the 

 leaves were borne on the trunks, but no means 

 of 'determining which leaves belonged to which 

 trunks.* The dilemma is one existing in the 

 nature of things and can only be escaped 

 through further discovery. We certainly do 

 not escape it by multiplying classes. But as 

 the Cycadales and Bennettitales are already 

 recognized classes, a group that embraces them 

 both can not be a class. It may be called a 

 superclass. Mr. Seward's name has the form 

 given to much higher groups, such as the 

 Pteridophyta and Spermatophyta. It is in- 

 cluded under the latter, and, therefore, should 

 have a different termination. The reasons for 

 such a group given by ISTathorst and Seward 

 are not sound, and the group name seems 

 useless. 



Much the largest number of species are from 

 the Oolite, viz., 42, as against 12 from the 

 Lias, and 5 from the Rhetic, and as these are 

 all additional to the 65 described in the first 



* Nineteenth Ann. Rep. U. 8. Geol. Surv., 1807- 

 98, Wasliingto^, 1899. p. C65. 



part from the Oolite of Yorkshire, it is evi- 

 dent that this is the great Mesozoic fiora of 

 Britain, and that the floras of other Mesozoic 

 beds are comparatively insignificant. But 

 this is largely the case in other parts of the 

 world. The greater number are from the 

 Great Oolite of Oxfordshire (Stonesfield). 

 Wiltshire ( Sevenhampton and Eyeford), 

 Gloucestershire (Chedworth) and Northamp- 

 tonshire (Kingsthorpe and Leckhampton). 

 The Inferior Oolite yielded nine species, the 

 localities being in Gloucestershire, Northamp- 

 tonshire and Somersetshire. Five species are 

 from the Oxfordian, which is represented in 

 Wiltshire (Christian Malford), Cambridge- 

 shire (Chippenham) and Northamptonshire 

 (Peterborough), as well as at Scarborough in 

 Yorkshire. Mr. Seward includes the Coral- 

 lian and Kimeridgian in the Oolite. The 

 former is represented at Malton in Yorkshire, 

 and has yielded three species, the latter at 

 Weymouth and Sandsfoot in Dorsetshire, and 

 contributes two species. 



The Jurassic flora described in Part II. 

 contains 18 conifers, 15 cycads, 2 Ginkgoales, 

 11 ferns, 1 lycopod, 2 Equisetales and 4 thallo- 

 phytes. Besides these there are described and 

 figured two leaves from Stonesfield which seem 

 to be dicotyledonous. As we can not question 

 the fidelity of the figures, and as these, so far 

 as the material shows, have every appearance 

 of dicotyledonous plants, the doubts must be 

 as to the source of the specimens, but Mr. 

 Seward says that the records clearly state that 

 one of the specimens at least is from Stones- 

 field, and that 'the rock appears to be iden- 

 tical with that in which the majority of the 

 Stonesfield plants are found.' He inclines to 

 think that the record is reliable, and that we 

 actually have ' a dicotyledon from rocks of 

 the Great Oolite Series.' This seems incred- 

 ible a priori, as thus far no dicotyledonous 

 plant has been discovered lower than the 

 Lower Cretaceous (Older Potomac) of Vir- 

 ginia. The figures recall those of Populus 

 primceva of Heer from the Kome beds of 

 Greenland (Urgonian), which was long the 

 earliest dicotyledonous plant known. They 

 differ, however, considerably from that type, 

 and as the lowest veins are not shown, there 



