424 



Correspondence — J. A. Bartrum. 



undulations must affect the level of the base of the Chalk, and in 

 constructing my map showing levels in the base of the Chalk I was 

 without adequate data concerning these anomalous levels in this 

 particular area. With the incorporation of a sufficiency of data in 

 the maps the final result would agree with field observations — and 

 while the data accumulate a faulty map is better than no map. 



H. A. Baker. 

 Afloat, 

 H.M.S. " Carysfort ". 

 • July 25, 1918. 



NOTES AND QUERIES FROM NEW ZEALAND. 

 SIr, — I am forwarding two photographs in which perchance some 

 of your readers may be interested. One represents the common 

 rhombohedral multiple twin of calcite, seen on a weathered surface 

 of the mineral, and the other an unknown fossil. [We omit the 

 description of the photographs, which is appended to the figures given 

 below. — Ed. Geol. Mag.] 



I have discarded all thought of inorganic origin for the "fossil" 

 on account of the great regularity and the successive layers shown, 

 but can offer no convincing suggestion as to the actual nature, and 

 shall be grateful for any information thereon. 



John A. Bartrtjm (Lecturer in Geology). 

 University College, 



Auckland, New Zealand. 

 May 6, 1918. 



Having referred Mr. Bartrum's photographs to our colleagues 

 Dr. G. F. H. Smith and Dr. F. A. Bather, of the British Museum 

 (Natural History), Cromwell Road, we have been favoured with the 

 following remarks thereon. — Ed. Geol. Mag. 





~7%W^. 









-C 



Vj*'"'.., 







Fig. 1 : Calotte Ci^eavage. — This shows clearly the crossing lamellae 

 seen on a weathered surface of a specimen of twinned calcite from 

 Port Waikuto, New Zealand. The lamellae are usually rendered 

 conspicuous owing to readier solution along the composition planes, 

 but occasionally it appears as if there has been differential solution 

 of the opposed sets of twin-lamellse. — G. F. H. S. 



