Correspondence — Professor T. G. Bonney. 287 



2. " The GraptoHte-Fauna of the Skiddaw Slates." By Miss G. L. 

 Ellas, (Communicated by J. E. Marr, Esq., M.A., F.E.S., F.G.S.) 



This paper deals not only with the collections of the author, but 

 with the Dover Collection and others preserved in the Woodwardian 

 Museum, with the collections of Professor H. A. Nicholson, Mr. 

 Postlethwaite, and that of the Keswick Museum of Natural History. 

 An account of the literature, both stratigraphical and palseontological, 

 of the Skiddaw Slates is given, followed by a list of all the graptolites 

 known from the beds. This list comprises 22 genera and 59 species. 



In the ensuing description all the known genera and species are 

 noted, and corrections and additions made to existing knowledge con- 

 cerning the diagnosis, structure, and development of many of them. 



The following seven species, new to this country — JBryogrnptus 

 rnmosiis (Brog.), Clonograptus tenellus (Linn.), Trochograptus diffusus 

 (Holm), Pterograptus (Holm) sp., Didymograptns gracilis (Tornq.), 

 Azygograptus suecicus (Mbg.), Diplograptus appendiculatus (Tornq. 

 MS.) — and ten new species and varieties are described. 



A table showing the distribution of the Skiddaw graptolites in 

 the Arenig rocks of Great Britain, in the Phyllograptus-QkiSer, etc., 

 of Sweden, and the Quebec Group of Canada is given, and the 

 accompanying (contracted) table (p. 286) expresses the relationships 

 of the divisions of the Skiddaw Slates with the rocks of these areas. 



In conclusion, the author is struck with the remarkable resem- 

 blances existing between the species of various genera ; these can be 

 so easily explained by supposing that the forms in question are the 

 results of development along certain lines, that she offers the 

 suggestion that this is their real origin. In dealing with the 

 phylogeny, she divides these graptolites into two groups — 



(1) Those derived from a Bryograptus-iovva. 



(2) Those derived from a Clonograptus-ioYxa. 



To the first group belong 15 named graptolites from the Skiddaw 

 Slates and 4 species from other localities ; and to the second 12 

 Skiddaw species and 2 others. 



coi^i^es:poitx)ed^C!e. 



THE LLANBEEIS UjS^CONFOEMITY. 



Sir, — As my name has figured much in your pages for the last 

 two months permit me to say that I have no intention of replying 

 to Mr. Blake's " Revindication of the Llanberis Unconformity." 

 My chief reasons for adopting this course are : (1) It would be 

 necessary for me to investigate on the ground all statements which 

 rest only on his authority, because hitherto I have so often found 

 that what he deems facts appear to me to be fancies. For this task 

 I have now no time, being tied much more closely to London than 

 was formerly the case, so that my short vacations are devoted 

 to work which offers greater attractions. (2) Controversy with 



