1849.] BOWERBANK ON A SILICEOUS ZOOPHYTE. 319 



the Oxford clay between the Wealden and the cretaceous series as 

 resulting from a drift, he remarks : — 



'* 1st. That I could not perceive in the fossils those marks of 

 abrasion which would indicate their having been drifted. 



" 2ndly. That the Oxford clay has considerable depth. It has 

 already been penetrated to the depth of about sixty feet without 

 reaching its termination. 



'' 3rdly. That the vertical surface of the wall of chalk is hardly 

 consistent with the natural results of previous diluvial action in that 

 locality. And, 



'* 4thly. In many places the theory of a drift may involve no phy- 

 sical difficulties. But at Ridgway this idea would involve serious 

 objections. Whence, it might be asked, could the Oxford clay have 

 been drifted ? The Oxford clay of Ridgway is about 200 feet above 

 that of Weymouth ; and the next exhibition of that bed on a higher 

 level would be at Little Bredy near Abbotsbury Common, at a di- 

 stance of between five and six miles, and at a level, I apprehend, 

 certainly far below that of Ridgway. Whatever difficulties may 

 therefore be supposed to attach to the theory which I have ventured 

 to propose, will not, I think, be diminished by the suggested explica- 

 tion of a drift. I have also satisfied myself by repeated and careful 

 examination that the section contains no double fault." 



3. On a Siliceous Zoophyte, Alcyonites parasiticum. 

 By J. S. BowERBANK, Esq., F.R.S. G.S. &c. 



Parkinson in his 'Outlines of Oryctology' has applied the term 

 Alcyonites to designate those fossils which were supposed to have 

 been polypiferous animals allied to the recent genus Alcyonimn. I 

 have therefore adopted that name as being the best designation of the 

 fosssil I am about to describe, although there is an objection to the 

 term from the very indefinite and promiscuous manner in which it 

 has been formerly used by authors ; and Mr. Morris, possibly for the 

 same reason, has judiciously excluded it from his ' List of British Fos- 

 sils.' However that may be, in the present case it is applied strictly 

 in accordance with the correct definition of the recent genus Alcy- 

 onium given by Dr. Johnston in the second edition of his excellent 

 and beautiful ' History of British Zoophytes.' 



The fossil which forms the subject of this memoir is not in its 

 natural and immutilated condition, but is a portion of the animal con- 

 tained in a small slab of agate 1^ inch long by 1-i- wide, such as are 

 commonly mounted in ladies' brooches. I obtained it from a dealer 

 along with a considerable number of specimens of what are generally 

 designated as Moss Agates. It is represented of the natural size, 

 Plate VIII. fig. 1, and a fibre magnified 100 diameters by fig. 2. 



