On some Eruptive Rocks from New Zealand. 267 



typical M. leinttvardinensis 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. Nilssoni and M. 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 

 Hocks 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 thecse 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 Monograptus and one species of Retiolites are new, and 

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

 of Monograptvs are arranged round type-species into six groups. 

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

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

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

 formations. Thus the supposed great palaeontological break between 

 the two Series to a great extent disappears. 



April 4th,— J. J. H. Teall, Esq., M.A., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' Additional Notes on some Eruptive Rocks from New Zealand/ 

 By Frank Butley, 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 pro- 

 cured from other localities in the North Island, including several from 

 Botorua. 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 obsidiaus, 

 with rhyolitic and pumiceous breccias and tuffs, geyserites, and 

 sinters. The rocks exhibit spherulitic and perlitic textures, 

 fluxion, devitrification, and impregnation with silica. In one case 

 the obsidian, after solidification, appears to have undergone the 

 following changes : — (1) devitrification, with formation of spheru- 

 lites ; (2) increase in temperature sufficient to destroy the double 

 refraction of spherulites and the earlier-formed felspars ; (3) the 

 decomposition of parts of the spherulites, causing them to assume 

 the characters of a coarse-grained felsite. The rocks from Botorua 



