
fi 
i 

80 B. N. A. BOUNDARY COMMISSION. 
both, being the form with globose chambers, and each having its rarer 
analogue, with chambers flattened and more delicate.* 3s 
182. The finer part of the softer portions of the rock, is composed 
almost entirely of the extremely minute bodies, which are included under 
the general names—Coccoliths and Rhabdoliths. These are now known to 
belong to minute pelagic vegetable organisms. Coccoliths.are abundant 
in most modern oceanic deposits, and have long been known to occur in 
the chalk of England and elsewhere, but do not appear to have been 
previously observed in the Cretaceous rocks of America. The allied 
Rhabdoliths were discovered by Dr. O. Schmidt in 1872, in the Adriatic 
Sea; but I do not know that they have heretofore been found in the - 
fossil state. These very minute bodies are well preserved in the 
limestone from Boyne River, and run through the same set of forms as 
those described by Dr. Schmidt. + (Plate XVIL., Fig. 1.) 
183. The limestone, where it occurs on the Boyne River, appears to 
be interleaved with beds of soft clay ; but the accounts I have received, 
are not sufficiently precise to enable any definite conclusions as to its 
thickness or extent, to be arrived at. Its occurrence at this one locality; 
enables the outcrop of the Niobrara Division—or highest bed of the 
Lower Cretaceous series—to be defined ata point nearly four-hundred 
miles further north than it has previously been known, and fixes the 
position of a well-marked horizon in the Cretaceous rocks of the North- 
west. f 
184. In the immediate vicinity of the forty-ninth parallel, no rocks 
referable to the Niobrara division are found along the escarpment of . 
Pembina Mountain, and their outcrop is no doubt concealed by the great 
thickness of sandy and alluvial deposits piled against its base. The beds 
here seen in place appear to belong to the 4th or Fort Pierre group of 
Meek and Hayden, which, in their Missouri sections, immediately over- 
lies the last, and forms the base of the closely associated group of Later 
Cretaceous deposits. From the scarcity of fossils in the great thickness of 
beds exposed in the Pembina Escarpment, and the want of information 
as to the nature of the Cretaceous beds intervening between these ex-— 
posures and those of the tributaries of the Missouri, caused by the thick 
*The microscopic organisms from this rock are described, and their relations more fully discussed, 
in the Canadian Naturalist., vol. vii., p. 252. +t Ann. and Mag. Nat. Hist., 1872. 
t Specimens since obtained by the Canadian Geological Survey, west of Lake Winnipegosis, seem to 
belong to the same division, and enables its outcrop to be traced still further to the north. See Report of . 
Progress, 1874-75. 
The rocks of the Niobrara division in Nebraska, are found to yield the best quicklime of any in the 
State, though Carboniferous limestones also occur there. 

