336 Correspondence. 



than Bunter times, for there is no reason to believe that the Derby- 

 shire limestone was 'under water from the end of the NewEed Sand- 

 stone period till the Grlacial epoch, and very likely not even then ; 

 and if any outliers of Bunter beds were left upon the Mountain 

 Limestone, similar deposits might be forming at the present day. 



I am also far from certain that the Eibden deposits are overlaid by 

 true Boulder-clay ; what I saw looked quite as much like the cover- 

 ing, often many feet thick, of local rain wash, which spreads over the 

 hill country thereabouts. Of course, some of this may be of the 

 same date as Boulder beds, some is very likely much older, and it is 

 forming now-a-days after every shower of rain. 



Yours obediently. A. H. Geeen. 



Monk Bketton, Baensley, June 3rd, 1867. 



GKAPTOLITES. 

 To the Editor of the Geological Magazine.' 



Sir, — Dr. Nicholson's paper in your last number might suitably 

 have closed the correspondence which you have published between 

 us, but I must ask you for permission to add a word or two. 



Your correspondent gives up the relation between the capsules 

 and the graptolites, as originally figm^ed by him, to which I objected, 

 and on which he based the whole of his argument for their being 

 ovarian vesicles, and with this consequently that argument as well. 

 But he has, in the paper in your last number, figured several speci- 

 mens which prove "conclusively that there is an actual organic con- 

 nection " between the capsule and the zoophyte. What do these 

 specimens show ? On the one species, Graptolitlms Sedgwickii, he 

 finds the " ovarian capsules " borne on the common coenosarc (PI. 

 XI. fig. 16) as well as developed from individual polypites ! and in 

 the latter case the polypite sometimes is converted into an '' ovarian 

 capsule" (fig. 15) the mouth of the hydrotheca narrowing into and 

 being " organically connected " with the capsule, and at other times 

 gives origin to the capsule from the sides of the hydrotheca ! (fig. 

 12-14). The only thing that I know at all comparable to this extra- 

 ordinary structure is the " ovisac " which is thus so strangely related 

 to the parent, which Dr. Nicholson tells us is a corneous gonophore 

 that becomes a free swimming zooid ! 



Wm. Cabrutheks. 



Note. — Prof. Harkness requests that the following corrections 

 may be made in his letter, which appeared in our last Number at p. 

 286. In the heading to his letter for " Upper " read " Lower Llan- 

 dovery," and in the fifth line, for "about" read "above the position." 



