Thomson. — Geology of Middle JVaipara and Weka Pass District . 367 



In a tributary draining from Mount Brown unconformable contacts of 

 these gravels with the underlying Greta beds are clearly exposed. In 

 some cases the lowest bed of the Kowhai series rests on a surface obliquely 

 truncating several beds of the Greta, series. In other cases the surface of 

 contact is with a single bed, but shows clear evidence of erosion in its 

 irregular contours. 



PAET II.— DESCRIPTIVE PALAEONTOLOGY. 



Considerable, collections of fossils were made by McKay and other 

 member* of the Geological Survey, but came chiefly from the Piripauan. 

 In 1912 and 1913 I spent several weeks in the district supplementing 

 these collections, especially from Tertiary horizons, as a result of which I 

 announced in 1913 that " although a classic locality for the determination 

 of the relationships of the Cretaceous and Tertiary beds, the Middle Waipara 

 and Weka Pass district is not well suited, owing to its poverty in molluscs, 

 to become the standard of reference for the Tertiaries of New Zealand." 



The description of the saurians by Owen, Haast, Hector, Lydekker, 

 and Hutton has already been mentioned in the account of the exploration 

 of tlie district. The Piripauan Pelecypoda were described in a palaeonto- 

 logical bulletin by Woods (1917), while the Gasteropoda were forwarded 

 before the war to Professor Wilckens, of Jena, now of Bonn, and their 

 description has been delayed. The Tertiary Mollusca were determined by 

 Mr. H. Suter, who described the new species in 1917. The fish-remains, 

 both Cretaceous and Tertiary, were described by Chapman in 1918. More 

 recent collections, in 1915 and 1919, have been determined by Mr. P. G. 

 Morgan. The Foraminifera were also forwarded to Mr. Chapman, and 

 he is preparing a palaeontological bulletin on this group. A few of the 

 Brachiopoda have been noticed in my earlier papers on this group, and to 

 render this account more complete a reference to these is given below, 

 together with descriptions of the new species. The echinoids, cirripedes, 

 and Polyzoa have not yet been determined, but there is little good material 

 in these groups. 



TERTIARY MOLLUSCA. 



An attempt has been made to use the most recent nomenclature, and 

 many of the names employed by Suter have been rejected on account of 

 the criticisms by Iredale, Smith, and Hedley. From a geological j)oint of 

 view these frequent changes in the names of common species are deplorable, 

 but are a sign of the renewed activity in the study of the group. From 

 a scientific standpoint there is no justification for neglecting any proposed 

 change which bears on the face of it evidence of its correctness, and one 

 can only hope that finality will soon be attained. In such a case as the 

 species of the Volutidae, where the changes of generic appellation have been 

 numerous, and authorities still difier, 1 have deemed it best to retain the 

 original name Valuta. A few notes on individual species are appended. 



Sella chathamensis Sut. var. 



A specimen was obtained from the Greta beds of the Waipara River, 

 on which Mr. Suter remarked in 1913 that it was more cylindrical than 

 Recent examples. He added that this was the first record of this species 

 fossil. 



