170 DR. c. T. teechma:n^n on [vol, Ixxiii,. 



comparable in every way with faunas of similar age in the great 

 circum-Pacific region. It is now well established that Trigonia and 

 belemnites of the Atractites Sind Aulacoceras group are normal associates 

 in the marine Triassic beds with such Palgeozoic survivors as Orthoceraa 

 and Dielasma. It is the association of Palseozoic survivals with the 

 Mesozoic forerunners which gives a special interest to the Trias. 

 Such archaic survivors at the present day as exist in New Zealand are 

 chiefly fcund in the terrestrial fauna and flora owing to its long isola- 

 tion as a land-mass. 

 g. There is no premature appearance of truly Jurassic forms in the New 

 Zealand Trias, The supposed Gnjiolisea - which has been mentioned 

 in this connexion is a shell allied to that called Mytilus 'prohleinaticxis.. 



III. LiTHOLOGT, Thickness, and Tectonics. 



The Trias consists of a great series of coarse or fine felspathic 

 sandstones, grey or dark shales, and argillites — some very hard, 

 others, when weathered, of a splintery or crumhling nature, fre- 

 quently enclosing concretions. Thick beds of coarse conglomerate,, 

 more or less discontinuou.s and lenticular, appear at various horizons. 

 Thin bands of pebbles also occur in the felspathic sandstones and 

 greywackes. Prof. Marshall ^ has examined the pebbles composing- 

 some of the conglomerates, and notes the absence of schistose 

 rocks. They are made up of granitic or porphyritic fragments 

 with felspar- and quartz-pebbles. 



The Ilhaetic beds become more pebbly and glauconitic and less- 

 felspathic, approaching in character the overlying Jm-assic series. 

 In some beds the quantity of felspar is so great that the rock 

 weathers along the joint-planes in large spheroidal masses, and has 

 given rise to the term •' cannon-ball sandstone.' Iron-stained beds 

 containing plant-remains occur interbedded with the marine series 

 at several places. 



No definite assertion can yet be made as to the source whence the 

 material of the Trias was derived, but there was evidently some large 

 land-mass not far away. The series seems to agree closely with 

 the littoral facies of the Trias on the south-western coast of New 

 Caledonia. The littoral nature of the sediments explains the 

 absence or rarity of certain fossils, such as ammonites and corals. 

 Except in the Okuku district, where diabasic ash-beds are reported 

 to occur (but these, if re-examined, would probably turn out to 

 be felspathic sediments), no contemporaneous igneous rocks are 

 known in the Trias. A dyke occurs at Nugget Point,^ and a 

 hypabyssal intrusion at Kawhia '^ ; lut these are probabl}^ of 

 post-Jurassic age. 



No natural base of the Trias is seen in any of the localities 

 .described, although in the Takitimii Mountains, west of the 

 Hokonuis, the Kaihiku is said to rest unconformably upon the 

 Maitai Series.-^ 



1 Bibliography, 22, p. 22, ^ Bibliography, 23. 



^ Bibliography, 45. ■* Bibliography, 30, 



^ Bibliography, 15, Introduction, p. -sii. 



