KIRKBY — SANDPIPES IN MAGNESIAN LIMESTONE OF DUEHAM. 293 



and I need only remind yon of M. Gmenewalds' papers on Bogoss- 

 lowsk. At tlie locality Petropawlowsk the proportion of tlie total 

 BracMopoda and Corals to all the rest of the fossils is twenty-six to 

 one, or nearly seven and a-half to one ; at Bogosslowsk eighteen to 

 one, or two. In the middle zone, as given by the fossils common to 

 the "colonies" and E in Bohemia, this proportion on the contrary is 

 twelve to forty-eight, or one to four. At Bogosslowsk and Petropaw- 

 lowsk not one member of gronp A is fonnd ; not even a single Orthis. 



M, Barrande, in his paper on the parallel between the Silnrian 

 deposits of Scandinavia and Bohemia, has shown that during the 

 first periods of animal life, the species were already not universally 

 spread, but distributed according to the same strict rules which regu- 

 late the distribution of organic beings in our days. Convinced as I 

 am of the correctness of this view, I venture to add that in remote 

 times also the distribution of the species was not only horizontally 

 but also vertically limited, i. e., that not only geographical provinces 

 but also bathymetrical zones have existed in the Silurian seas. 



In closing this abstract, I beg you, my dear friend, to remark, 

 that for the sake of shortness some view may be put forth here 

 too apodictally, which is only enounced as a mere conjecture in my 

 paper, and many an argument in favour of my views has been 

 omitted ; I beg also to observe this to any one of your friends, to 

 whom these lines might seem to you worth communicating. Impos- 

 sible as it is to arrive at decided conclusions by the study of one single 

 class, I have only intended to show that fossils may no more be re- 

 garded as mere " dead-born medals," but must always be looked upon 

 as the remains of living beings, the existence of which depended 

 upon a thousand external conditions. 



I am, my dear friend. 



Most truly yours, 

 To Thos. Davidson, Esq., F.Q-.S. Edw. Suess. 



ON THE OCCURRENCE OF " SAND-PIPES " IN THE 

 MAGNESIAN LIMESTONE OP DURHAM. 



By J. W. KiRKBT. 



During the past year my attention has been directed to some 

 curious tube-like cavities in the magnesian limestone near Sunder- 

 land, which I beheve to be perfectly analogous to the sand- and 

 gravel-pipes of the chalk districts of the south of England and 

 France. And as our knowledge of such pipes has hitherto been 

 almost confined to their occurrence in the chalk, I deem it advisable 

 to describe these in the magnesian limestone ; not that they add 

 much to what we already know, or that they afibrd grounds for a 



