AXNIVEBSAET ADDRESS OF THE PRESIDENT. 



187 



Nautilus. — The European area, so rich in the 4 genera previously 

 noticed, is unexpectedly poor in Nautili, not more than 11 species 

 having been described therefrom, and only 4 or 5 from America. 

 We possess only 2 species, N. germanus and N. megasipho ; the 

 former Middle Devonian, Torquay, the latter Upper Devonian, from 

 Petherwin. 



Poterioceras. — Only in the Upper beds at Petherwin is this genus 

 represented, and by 1 species (P. fusiformis) : it also passes to the 

 Carboniferous rocks. The analysis of the Devonian Cephalopoda and 

 their distribution show that the British species number 60, belonging 

 to the 6 genera I have separately discussed. Only 1 is Lower Devo- 

 nian; the Middle Devonian has yielded 4 genera and 33 species, and 

 the Upper 5 genera and 33 species. 



Looking, then, at our small Devonian Cephalopod fauna (6 genera 

 and 60 species) as compared with that of Europe (20 genera and 500 

 species), which alone nearly equals all the species in the 14 classes 

 in the British Devonian rocks (544), we readily see the value of 

 this fauna in Europe, Belgium, the Eifel, the Harz, Saxony, 

 the Eichtelgebirge, Russian Poland, Russia in Europe, and Spain. 



In Belgium, Prance, the Eifel area, the Eichtelgebirge, and Saxony, 

 the Devonian group, as with us, readily falls under the 3 divisions of 

 Lower, Middle, and Upper, and in the main the grouping corresponds 

 or maybe correlated with our own. In Belgium (south of the Condros) 

 the Psammite of Condros, the schists of Pamenne, and the limestone 

 of Erasne are the equivalents of our Upper Devonian as exhibited 

 at Petherwin in Forth Cornwall, and the Baggy, Pilton, Brushford, 

 and Marwoodbeds. The " Givet Limestone" at the summit of the 

 Middle group is the equivalent of the Stringocephalus-heds of Xorth 

 Devon, but with us stratigraphically lower. 



The CaJceola-schists and the (Spirifer) " OultrijugatusSisa£e " 

 of Belgium are our C ale cola-heals of Torquay and Xewton in South 

 Devon, and the typical Middle Devonian. The schists of Burnot, 

 Ahrian, and the Coblentzian and Gadinian correspond with the 

 Linton and Lower slates and grits of North Devon — our Lower 

 Devonian (the lowest probably not seen). In the Eifel area, the 

 beds of which, like the deposits of Belgium, correspond so closely 

 with our own, the Goniatite-schists and (EliynclioneUci) Cuhoides- 

 limestone are, like those of Xorth Cornwall and Devon, the upper 

 division : and, as in Belgium, the Calceola-schists and Cultrijugatus- 

 Stufe are the equivalents of the South-Devon limestones or Middle 

 Devonian : theYichter schists, Ahrian (of Dumont), and the Coblentzian 

 beds represent the mass of the lower shales, slates, and grits below 

 the Hangman beds in Xorth Devon. M. Gosselet*. in his succession 

 of the Devonian rocks of Xorth Erance and Belgium, divides the 

 whole into 6 divisions or beds. The corresponding rTorth-Erench 

 beds to our Upper Devonian are probably the Psammites of Condros, 

 the slates of Eamenne, and the Boulonnais beds. 



The Givet Limestone andgCalceola-slates are our Middle Devonian, 

 and the systeme Ehenan the Lower. 



* Bull. Soc. Geol. de France, vol. xviii. p. 18. 



