The Niobrara Chalk. — Calvin. 155 
under water in a shallow dish, decanting and renewing the 
water as long as gentle rubbing of the heavier residual mate- 
rial produces any traces of milkiness. The particular genera 
and species that will be found after the washing process is 
complete will depend somewhat on the locality from which 
the specimen under investigation was derived. Even at the 
same locality samples of chalk from different beds will be 
found to differ in a marked degree so far as relates to the 
presence or absence, the association, or the predominance, of 
certain types. It would be very tedious, unprofitable and 
altogether aside from my purpose, to give you a catalogue of 
the genera and species of the foraminiferal fauna. Indeed, 
according to Carpenter, Brady, and other authorities, species 
in the sense of constant!} 7 differentiated races do not exist 
among Foraminifera, and it is almost impossible to define 
genera; but some general statements, which may lead to sci- 
entific considerations of some importance, maybe possible and 
permissible under the circumstances. 
The Foraminifera, with Observations on their Distribution. 
Saint Helena, Nebraska, seems to me to be the most typical 
locality in the region under consideration. In samples of 
chalk from this locality large forms of Textulaiua globulosa of 
Ehrenberg are the most common and the most characteristic 
fossils. Here the species presents its ideal characteristics. 
The chambers are inflated and spherical, and the shell is ro- 
bust and widens rapidly toward the larger end. This same 
shell, be it remembered, ranges throughout the Niobrara of 
America from Texas to Manitoba, and it is one of the most 
conspicuous forms at certain horizons in the chalk of Europe. 
Associated with Textvlaria globulosa is a smaller shell that is 
proportionately thinner and narrower and every way less ro- 
bust. In some places this Bmaller f orm is the prevailing type. 
It has been regarded as a distinct species, and was figured by 
Dawson, in the paper already cited, undei he name of Textu- 
laria pyyincua. While these two forms gr,\ ie into each other 
perfectly when a sufficient number of specimen-- i- examined 
it will be profitable for the present to keep them apart, inas- 
much as the distribution of the two types presents some facts 
worthy of consideration. Recall for a moment the geograph- 
ical and bathymetrical conditions of the region while the chalk 
