178 Reviews — Block Mountains in New Zealand. 



PLATE II. 



Fig. 



1. Pronorites aff. cydolobus (Phill.). x 1|. 



2. Pleurotomaria (Mourlonia) aff. conica Phill. X IJ. 



3. Euomphaliis cf. subcircularis Mansuy. x 2. 



4. Helminfhochiton cf. priscus (Miinst.). x 2. 



5. Parallelodon aff. corrugatus De Kon. X 1^. 



6. Edmondia sp. x 2. 



7. Posidonomya Becheri Bronn, var. siamensis nov. x l-i. 



8. Pseudamusium cf. prcetenue (Von Koen.). X 1^. 



9. Aviculopecten cf. densistria (Sandb.). x 2|. 



10. Athyris subtilita Hall, x IJ- 



11. Camarophoria sp. X 2. 



12. Ditto. X IJ. 



13. Productus concentricus Sarres-Kayser. X 3. 



14. „ lavipunctatus Sarres. x 3. 



15. Chonetes cf. rectispina Von Koen. x 2. 



16. „ aff. buchiana De Kon. x 2|. 



17. Proef.us cf. roddonensis Woodw. X 3. 



18. Phillipsia aff. silesiaca Scupin. x 5. 



19. Cladochonus cl. Michelini Edw. & Haime. x li. 



REVIEWS. 



Block Mountains in New Zealand. By C. A. Cotton. Amer. 



Journ. Sci., vol. xliv, 1917, pp. 249-93. 

 nPHIS pamphlet deals more especially with the block mountains 

 -^ of Otago, a district in which the block features are unusually 

 well preserved. The upland surfaces in Central and Eastern Otago 

 have been described by both Park and Marshall as portions of 

 a dislocated plain of erosion, termed a peneplain, the present relief 

 being regarded as the work of erosion. 



The writer's hypothesis, however, involves planation, sedimen- 

 tation, and deformation, followed by a period of erosion, during 

 which larger areas of the planed undermass have been re-exposed 

 by stripping of the cover. It is quite possible that some of the 

 eroded surface of the undermass has never been covered, and there- 

 fore forms a true peneplain ; but, to the writer's mind, conclusive 

 evidence as to the former wide extension of an overmass is afforded 

 by the occasional preservation of small outliers of the cover on the 

 upland plateaus ; by wide distribution of the " sarsen stones " 

 derived from the cemented quartz grit ; and by the manner in which 

 planed surfaces of the older rocks emerge from under brown coal 

 strata as well as quartz grits with the same inclination. 



Stress is laid on the fact that fault scarps form the boundaries 

 of a number of blocks in Central Otago, and sufficient evidence of 

 faulting is furnished by the attitude of the covering strata at the 

 bases of the scarps. The conclusion arrived at is that the relief 

 is very largely — almost entirely— due to recent differential movement 

 of crust blocks. 



H. V. S. 



