No. 5.] 



DAWSON — FORAMINIPERA, MANITOBA. 



253 



and clay, indicating comparatively shallow-water conditions, and 

 the proximity of land. The nearest approach to chalk is found 

 in tlu' interior continental basin, especiall;: where the Cretaceous 

 rocks are finely exposed along the ?'8Ssouri Iliver, and where in 

 Hayden's third group or Niobrara division a soft white shelly 

 limestone occurs. It forms bold bluffs on some parts of the 

 river, and the name '* chalk" is popularly applied to it, and is 

 justified by the fact that it contains largo numbers of Foramin- 

 iferii, some of which froTii the Cretaceous of the Missouri and 

 Misf^issippi have bcun described by Ehrenberg, 



In 3Ianitoba, the rocks of the Cretiiccous Series are much 

 masked by drift material, and do not in any place I have seen 

 jield fossils in any quantity Through the kindness of Mr. A. 

 T. llussel, I have however received specimens from a locality 

 about twenty miles north of the 49tli parallel, on the escarpment 

 called Pembina Mountain, which exactly resemble the so-called 

 " chalk " of Nebraska, and contain interestinir or<:anic remains. 



The greater part of this rock is composed of shells of Inoce- 

 rami and oysters, the latter probably identical with Ostrea con- 

 </esfa, characteristic of the Niobrara division further south. 

 These shells are imbedded in a soft whitish earthy matrix, 

 which on microscopic examination proved to be rich in Forami- 

 nifera, Coccoliths, and allied organisms. 



X JOO 



Fig. 1. Foraminifera from the Cretaceous of Manitoba, 

 (a) Textularia globulosa. (i) T. pygiiiwa. (c) Uiscorbina globularis. 

 (d) Plai >rbulina Ariniineusis. 



The commonest foraminifers belong to the genus Textularia, 

 and represent two of its varieties. Of these the predominant is 

 a stout form with globose chambers rapidly increasing in size at 

 each addition, and sometimes even as broad as long. The pri- 

 mordial chamber, and those next it, are often bent away several 

 degrees from the axis of symmetry of the larger part of the shell. 

 The surfaces of the chambers are marked with extremely minutQ 



