Carruthers — On a Fossil Cycadean Stem. 199 



summing up the evidence in regard to the Quaternary gravels. He 

 is of opinion that the large pachyderms lived down to the commence- 

 ment of the alluvial period, and on that supposition says, " I do not 

 see any geological reasons why the great extinct mammalia should 

 not have lived down to comparatively recent times, possibly not 

 farther back than 8,000 or 10,000 years ago." In other words, he 

 puts that period as having elapsed since, as I understand him, the 

 last submergence of our lower valleys took place. 



According to my views this submergence would have passed away 

 in about a quarter of the term of 10468 years, subsequent to the 

 epoch 11020 — that is, about 8,000 years ago. This is, to say the 

 least of it, a remarkable coiacidence. 



II.— On Ctcadoidsa Yatesii, a Fossil Cycadean Stem from the 



PoTTON Sands, Bedfoedshire. 



(PLATE IX.) 



By Wm. Cakrutkees, F.L.S., of the Britisli Museum. 



WHEN examining the collections of the Geological Society at the 

 time of preparing the notes I published some months ago, on 

 the Fossil Cones of the Secondary Strata, I found a small fragment of 

 a curious vegetable organism, the nature of which I was then unable 

 to determine, but which I was allowed by the kindness of the 

 Secretary to take with me for the purpose of further examination. 

 Some months ago I obtained from James Yates, Esq., a more perfect 

 specimen, which clearly showed that it was the portion of the stem 

 of a cycadean plant, as Mr. Yates had already determined. Professor 

 Church subsequently brought me a jet finer specimen from the 

 Museum of the Eoyal Agricultural College at Cirencester, and I have 

 a fourth fragment from the collection of Professor Morris. 



All the specimens were found in the iron and green sands of 

 Potton, which rest on the Kimmeridge and Oxford clays, and are 

 covered by the Gault. Mr. Seeley, who has paid some attention to 

 these beds, kindly informs me that he considers them to " represent 

 in their upper part the Lower Greensand, which part is generally un- 

 fossiliferous ; the middle part is very rich in fossils, including many 

 vegetable remains, such as fir and other cones, wood, etc. These beds 

 are regarded as a marine representative of the Purbeck and Wealden 

 period ; and at the bottom are the representatives of the Fan-ingdon 

 gravels, and unfossiliferous sands." The Cycadean stems are found in 

 the middle part of the sands. They are converted into a rich brown 

 hematite, containing a larger proportion of iron than bog iron ore. 



Mr. Pettit drew the attention of the Geological Society to these 

 stems at its meeting on December 2nd, 1857, when he laid some 

 fine specimens on the table. He referred them to GlatJiraria ; but no 

 description of them was published, nor further notice taken of them. 



Professor Morris had had his attention directed to this fossil some 

 years ago, and having seen the fine specimen at Cirencester, he came 

 to the same conclusion as Mr. Yates regarding its affinities. 



It must be referred to Buckland's genus Cycadoidea = MantelUOf 



