440 Transaction^. — Geology. 



The general facies of the Trias in Nelson and southern 

 Otago exhibits a harmony that seems remarkable considering 

 the great distance which separates the localities. Near the 

 base of the formation in each place occur claystones with Ha- 

 lohia and Spiriferina, and in both places the Trias formation 

 is closed by an Athyris horizon, followed conformably by a 

 great series of claystones and sandstones. In Otago the for- 

 mation conformably overlying the Trias series is known as 

 the Mataura formation, to which a Jurassic age has been 

 ascribed by Sir James Hector and Captain Hutton. 



The natural inference to be drawn from the stratigraphical 

 evidence is that the Maitai formation of Nelson must be cor- 

 related with the Mataura series of Hutton. 



The Athyris bed at the top of the series contains thou- 

 sands of finely preserved Athyris and a few Spiriferina (Bas- 

 telligera of Hector). The Proditctus of the so-called Productus 

 formation of Mr. McKay at Nugget Point''' was found on ex- 

 amination to be a Sjnriferina. 



As there is no reason to believe that the Trias formation 

 in both Otago and Nelson has been overturned, we must 

 conclude, from the stratigraphical and palaeontological evi- 

 dence, that the so-called Permian beds of Mr. McKay in 

 Eighty-eight Valley occur at the top of the formation, and 

 are the horizontal equivalents of the limestone m the Wairoa 

 Gorge. 



The characteristic fossil of the Maitai formation in Nelson 

 is Inoceramus, which has been found in many places in tiie 

 lower horizons of that formation on both sides of the great 

 synclinal fold. This form occurs sparingly in the limestone 

 at the base of the formation {i.e., top of the Trias), but is 

 found in great abundance in slaty claystones about 100 ft. 

 above the Maitai limestone in the Maitai Valley and Dun 

 Mountain sections. 



I will now review the palosontological evidence bearing on 

 the correlation of the highest fossiliferous zone m Well's 

 Creek with the highest zone in the Shaw Bay section. I 

 have already shown that stratigraphically they both occupy 

 the same relation to the underlying Mi/tilus beds. 



Among the Brachiopoda from Well's Creek there are two 

 very characteristic genera — namely, a Spiriferina with singu- 

 lar comb-like dentition along the hinge-line, and an unusual 

 form of Athyris, represented by two species the general 

 features of which have already been described. The Spiri- 

 ferina is the Rastelligera of Hector, while the Athyris is 

 probably the Glavigera of the same author. f 



• Reps. Geol. Expl., 1873-74, p. 03. 



t Trans. N.Z. Inst., vol. xi., 1878, p. 538. 



