146 Dr. E. M. JR. S/iakespear — New Zealand Graptolites. 



and both, on the footwall and hanging wall of the reef itself in the 

 workings." They are confined to the fine textured slates, the coarser 

 ones being quite unfossiliferous. 



According to Mr. Bell (loc. cit., p. 34), the Aorere rocks in this 

 district are as a whole "folded into a great synclinorium," but the 

 "plication of the strata has been enormous, the rocks having been 

 folded into a series of very closely compressed troughs and arches, 

 which have a general trend of about north-north-west, with many 

 variations from regularitJ^" At the locality where the graptolites 

 were obtained the dip of the beds is about 30° to the west. 



Mr. Isaacson states that all the graptolites in his collection came 

 from the one band. It is, however, possible to distinguish two 

 main rock types, namely : («;) a somewhat coarse shale with an 

 irregular fracture, and {h) a fine, smooth, well-laminated shale. 



In the first of these («) I have identified the following species : — 



Bryograptus Laptvorthi, Ruedemann, Diploffrapius sp. (?). 



Bichograptiis octobrachintus, Hall. Gonioijraptiis perjlexilis, Euedemann. 



Didymograpttcs exlensiis, Hall. Loganographts Logani, Hall. 



B. gibberulus, Nicholsoa {caduceus, Fhyllograptits Anna, Hall. 



Salter). Fh. ilicifolius, Hall. 



D. nitidus, Hall. Tetragraptus Aniii, EUes & Wood. 



In the second {b) I have recognised — 



Bryograptus Lapivorfhi, Euedemanii. Phyllograptus typiis, Hall. 



Didymograptus affinis (?), Nicholson. Stropltograptus trichom<nics{?) Jiue^evn^jm. 



D. nanus, Lapworth. Tetragraptus Bigsbyi, Hall {similis, Hall). 



D. similis (?), Euedemana. T. cf. pendens, Elles. 



Goniograptus geometricHs, Ruedemann. T. quadribrachiatus, Hall. 

 Phyllograptns Anna, Hall. 



Intermediate in character between these two extreme rock types 

 there are a few slabs of shale, readily distinguishable by the mode of 

 preservation of their contained graptolites, which have yielded 

 Didymog. nanus, Phrjllog. angustifoUus, Phyllog. Anna^ and Tetrag. 

 Bigsbyi. These, however, may be grouped with {V). 



Thus the two types of rock are distinct, not only lithologically, 

 but also palaeontologically, and in this one collection there are 

 represented two different graptolitic zones or sub-zones. Either, then, 

 these two gi'aptolitic zones occur within the one carbonaceous band of 

 a few inches in thickness, or there is more than one graptolitiferous 

 band in the neighbourhood of the reef. Without further information 

 it is impossible to decide between these two suggested alternatives, 

 but the evidence brought forward by Mr. Isaacson and Mr. Bell as to 

 the movement that the rocks have undergone, and the occurrence 

 of the graptolites both on the walls of the reef itself and in its 

 neighbourhood, seems to be in favour of the possibility of there being 

 two distinct graptolitiferous bands present. 



The fauna of the band (a) is characterised by the abundance of the 

 species Didymog. gibberulus. It is undoubtedly the same fauna as that 

 described by Mr. Bell ; and if we except his identification of Rastriies 

 (which may be a fragment of Oo7iiograptus perjlexilis) the assemblage 

 of graptolites is that which one might expect. The forms which he 

 doubtfully refers to Climacograptus and Biplograptus may belong to 

 one and the same species ; and from an examination of the one or two 



