Geoh)(jlcal Suciet//. 427 



PROCEEDTXGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



May 4th, 18'J8.— W. Whitaker, B.A., F.ll.S., 

 President, in the Chair. 



The following communication was read : — 



' The Graptolite-Fauna of the Skiddaw Slates.' 

 By Miss G. L. Elles. 



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 Prof. H. A. Nicholson, Mr. Postle- 

 thwaite, and that of the Keswick Museum of Natural History. An 

 account of the literature, both stratigraphical and palaeontological, 

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

 lites 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 existiug knowledge 

 concerning the diagnosis, structure, and development of many of 

 them. 



The following 7 species, new to this country, — Bryoqraptus 

 ramosus (JBrtig.), Clonograptiis Unelhis (L\nn,)^ Irochograptus dljft(sns 

 (Holm), PteroyrajJtus (Holm) sp., LvJymogrcqjtus gracilis (Tqt.), 

 Azygograptus suedcus (Mbg.), Diplograptas appendiculatus (Torncj. 

 MS.), — and 10 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-'^k.iSer, etc., 

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

 accompauying (contracted) table (p. 428) 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 80 easily explained by supposing that the forms in question are 

 the results of development along certain lines, that she offers the 

 Buggestion that this is their real origin. In dealing with the phvlo- 

 geny she divides these graptolites into two groups : — 



(1) Those derived from a Bryograptus-iorxa. 



(2) ,, „ CIoi\ograp>tns-iovm. 



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. 



