well exposed at tlie Ridgway railway cutting. The 

 most eastern evidence of the Purbeckian forest in 

 Dorsetshire is at Gad Cliff, on the western side of 

 Kimmeridge Bay, where a magnificent trunk lies among 

 the debris of rocks, at its foot, encased in a limestone 

 shroud ; these base-beds of the series occur again 

 at Tisbury ; Doctor Buckland records them at Thame, 

 in Oxfordshire, and Doctor Fitton in the Vale of 

 Wardour ; they appear at Swindon, on the top of the 

 Portland beds, containing conifers and a few 

 examples of Mantellia. 



In 1854 there were only seven genera of cycads 

 known, in connection with the secondary rocks of Great 

 Britain. Mr. Carruthers, in his important and exhaustive 

 memoir* on fossil cycadean stems of that period, read 

 before the Linnean Society in 1868, retains the nomen- 

 clature of two genera only — Mantellia and Biicklandia 

 — and establishes four new genera — Yatesia, Williams- 

 onia^ Bennettites, and Fittonia, including eight new 

 species ; two new species are added to Bucklandi and 

 two to Mantellia. Six of the twenty-two species 

 enumerated by the author of the memoir have been 

 found in Dorsetshire, 



Yatesia gracilis., Carr, 



Bennettites Portlandicus, Carr, 



Mantellia nidiformis, Brongn, 



M. intermedia, Carr, 



M. Micro])hylla, Miq, 



M. pygmcea., Carr. 



* Traneactions of the Linnean Society, Vol. xxvi., pp. 675-708. 



