ANNIVERSARY ADDRESS OP THE PRESIDENT. 



147 



24 species of Graptolites, 13 of which are so derived. These are 

 associated with 1 from the Skiddaw and 8 peculiar to the Hudson- 

 lliver deposits. Nicholson, in his fifth, or Saxon and Bohemian area, 

 endeavours to show that two great migrations of Graptolites took 

 place from the area of the south of Scotland at the close of the Upper 

 Llandeilo period, one westward through Ireland to America, the other 

 southward into the north of England ; and he suggests a third migra- 

 tion from the same area in a south-easterly direction, or into the Silu- 

 rian seas of Saxony and Bohemia. Geinitz, in his " Grauwackenfor- 

 mation " of Saxony, believed the Graptolitiferous rocks to be the 

 summit of the Lower Silurian series (Llandovery). Of 5 genera and 

 12 species given, 4 genera and 10 species are derived from the Upper 

 Llandeilo of the south of Scotland, and 2 from the Coniston Mud- 

 stones. Barrande has recoguized the British derivation of the Bohe- 

 mian Graptolites (' Defense des Colonies,' 1870) ; he recognizes two 

 chief Graptolitic zones in Bohemia, viz. Etage D at the summit of 

 the Lower Silurian series, and Etage E at the base of the Upper. 

 The Bohemian Graptolites derived from Britain number 5 genera 

 and 14 species, and are believed to be derived through migration from 

 the Coniston Mudstones or Upper Llandovery beds of the north of 

 England. These are identical species with those which lived in the 

 mudstones named*. I hav^e thus shown that it is only in Scotland 

 and Cumberland that we obtain a Graptolitic fauna in the Llando- 

 very rocks (probably Lower), and that none occur in either of the 

 two Welsh areas f. 



Actinozoa. — The species of this class in the Lower Llandovery 

 number a fraction more than 2 to each genus, of which there are 12 

 (and 26 species). The genera Favosites, Heliolites, and Petraia abound 

 most in species — Favosites 5, Heliolites 4, Petraia 6. The distribution 

 for North Wales is 5 genera and 8 species ; for South Wales 8 genera 

 and 16 species ; and for Ireland the same number. Singularly just 

 as many species pass to the Upper Llandovery (20) as came up from 

 the Caradoc and Bala beds (20), and in each case 9 of the same 

 genera ; so that in reality the Lower Llandovery rocks possess only 

 6 species of Actinozoa peculiar to them, so closely allied are the two 

 formations through this, as through other groups of fossils. 7 of the 

 9 genera have as yet only yielded 1 species each. Nothing can be 

 more unsatisfactory than the evidence afforded by such scanty mate- 

 rials ; close research would result in yielding numerous and more 

 definite species. 



Echinodermata. — No species is known either in North Wales or 

 Ireland, and two species only in South Wales — Echinosphcerites 

 arachnoidea and Glyptocrinus, sp. (stem-ossicles). This last genus 

 occurs in Scotland also ; neither pass to higher formations, but the 

 same two species occur in the Caradoc. 



* Nicholson, loo. cit. pp. 228-230. _ 



f Recent researches by Lapworth into the specific value and history of the 

 Rhabdophora have tended to reduce the number of species, great numbers of so- 

 called species being established on mere fragments of other species. Their 

 elimination will be of great value to the student of this difficult class of the 

 animal kingdom. 



