278 Reports and Proceedings — Geological Society of London. 



In the Ludlow area the two lowest zones are rich in graptolites, 

 but shade into each other, and are thei'efore less clearly defined than 

 the higher zones, which each contain practically only one species 

 and are lithologically distinct. In the Builth area the variation 

 in the zones in different parts may be due to the conditions of depth 

 and current under which the graptolites have been deposited, or to 

 the overlap of higher beds on lower, as has been shown to be the 

 case with the Wenlock and old Eed Sandstone rocks. In the Long 

 Mountain syncline M. scanicus is practically absent, and the typical 

 M. Leintwardinensis of the highest zone has not yet been found, 

 although its place appears to be taken by a varietal form. Two 

 new species of graptolites are almost confined to this district. The 

 succession worked out in these districts is confirmed by that in 

 the Dee valley and the Lake District, but the evidence at present 

 obtained in the three other areas is only scanty. 



The Lower Ludlow sediments become thicker, coarser, and more 

 arenaceous when traced from the south and south-east to the north 

 and north-west ; but, in spite of this, there is a striking constancy 

 in the lithological sequence of the sediments. Only two of the 

 graptolitic zones, those of M. Nihsoni and 31. Leintwardinensis, are 

 present in all the districts. A table is given to show the distribution 

 of the graptolites in Britain and Europe, and one showing the order 

 of appearance of the graptolites of the formation. 



The Lower Ludlow graptolites present, as a whole, the following 

 peculiarities, and stand in marked contrast to those from the Wenlock 

 Kocks in the fact that while the polypary is straight for the greater 

 part of its length, it is distinctly curved inwards at the proximal 

 extremity. The apertures of the thecaB are for the most part either 

 spinose, or wholly devoid of ornamentation. The number of species 

 is eighteen, with thirteen varieties, of which six species and nine 

 varieties of Monograptns and one species of Betiolites are new, and 

 are described and figured in the paper. All the species and varieties 

 of Monograptus are arranged round tj'pe-species into six groups. 

 The richest groups in species and varieties are those of M. dnhrns 

 and M. coloniis. Most of these groups link the Ludlow Series with 

 Wenlock, and even the genus Betiolites is common to the two 

 formations. Thus the supposed great palceontological break between 

 the two series to a great extent disappears. 



XL— April 4, 1900.— J. J. H. Teall, Esq., M.A., F.K.S., President, 

 in the Chair. The following communications were read : — 



1. "Additional Notes on some Eruptive Eocks from New 

 Zealand." By Frank Eutley, Esq., F.G.S. 



The rocks described in this paper were, with a few exceptions, 

 collected by Mr. James Park. A few of the specimens come from 

 the area of the Hauraki Goldfields, but many of them were procured 

 from other localities in the North Island, including several from 

 Eotorua. The silica-percentages of several of the rocks have been 

 determined by Mr. P. Holland. 



The first part of the paper deals with twenty-three rock-specimens 

 and slides from them. These consist of rhyolites and obsidians, 



