XXVII. — On the Cycadeoidece, a Family of Fossil Plants found in the 

 Oolite Quarries of the Isle of Portland. 



By the Rev. WILLIAM BUCKLAND, D.D. F.G.S. F.R.S. F.L.S. 



PROFESSOR OF MINERALOGY AND GEOLOGY IN THE UNIVERSITY OF OXFORD, 



[Read June 6th, 1828.] 



About twenty years ago I saw for the first time specimens of these fossil 

 plants, in the collection of H. H. Henley, Esq. of Sandringham near Lynn. 

 They had been procured by him from the celebrated freestone quarries of the 

 Isle of Portland, where they were known to the workmen by the name of 

 petrified birds-nests, their external form bearing a rude resemblance to the 

 shape and size of a common crow's nest. 



My attention has been recalled to this subject by a communication which 

 I received in 1825 from Sir George Grey of Portsmouth, who transmitted to 

 me a similar fossil found also in (he Isle of Portland, and permitted me to 

 make the drawings of it represented in Plate XLVII. 



On my showing this specimen to Mr. Webster, he informed me that he 

 had presented two similar fossils from Portland to the Geological Society of 

 London*. There are also three more specimens in the museum of Mr. Sowerby, 

 two of which he has kindly permitted me to engrave in Plates XLVIII. and 

 XLIX. These specimens are all exclusively from the Isle of Portland. 



The mineral condition of these plants is almost entirely siliceous, varying 

 from coarse granular chert to imperfect chalcedony ; it resembles that of the 

 petrified trees which abound in Portland and often measure many feet both 

 in length and circumference, in some of which Mr. Brown has recognised 



* Mr. Webster informs me that he found these plants accompanied by large silicified trunks 

 of dicotyledonous trees, in a stratum which he designates by the workman's name of Dirt-bed, 

 being about one foot thick, consisting of a dark brown substance, and containing much earthy 

 lignite ; it lies immediately above the Portland building-stone, and divides it from slaty calcareous 

 beds, which Mr, Webster doubts whether to refer to the Portland or to the Purbeck series. See 

 Mr. Webster's paper on the Purbeck and Portland Beds, Geol. Trans. 2d series, vol. ii. Part I. 



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