Since Professor Macbride's paper on Bennettites dacotensis was published in the American Geologist for October, 1803, there have been numerous inquiries respecting the exact geological horizon from which the cycads were derived. The close resemblance and the intimate relationship indicated between the Dakota fossil and Tysonia marylandica Fontaine, while not conclusive, would point toward a common horizon for the two species, and so make it possible to correlate the Potomac formation with a definite Mesozoic horizon in the northwest. Professor Macbride's paper left the stratigraphical position of his species undecided. To settle, if possible, the question definitely the writer recently made a visit to the locality that furnished the types of Macbride's species.
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
"On the Geological Position of Bennettites dacotensis Macbride with Remarks on the Stratigraphy of the Region in Which the Species Was Discovered,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 18-22.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/9