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C. Term "Argiles fissilaires"- 1. Was not proposed as a formation name. [Form. S�d., p. 103, "Ces argiles fissilaires ne constituent pas un horizon d�termin�, car il yena dans le pyrother�en, dans le noto- stylop�en, dans le salamanqu�en, dans le p�huen- ch�en, et aussi dans les gr�s bigarr�s."] 2. Is a descriptive term ( and in a language foreign to the country in which the beds occur and to its author). 3. Is incorrectly descriptive, since the type of rock referred to is neither clay nor, in the exact sense of the term, fissile. The current use (by whom started?) for a definite stratigraphic unit between the Pehuenche and the Notostylopense is therefore undesirable. The "argiles fissilaies" may be: 1. A stratigraphic and temporal unit unrep- resented by any other type of rock, in which case it may be considered as a. A member of the Pehuenche Formation. b. A member of the Casamayor " c. An independent, intermediate formation for which the name Mazaredo Formation would be most appropriate. 2. A lithologic phase of the same age as rocks of different type elsewhere now placed in other formations, in which case it may be considered as or proven to be a. Equivalent to part of the Pehuenche of other localities, hence either ?. To be placed in the Pehuenche as a local lithologic member, or ?. To be separated from the Pehuenche with that part of the latter equivalent to it. b. Equivalent to part of the Notostylops beds of other localities + hence to enter into the Casamayor formation. D. Supposed association of dinosaurs + mammals. Probably due to these causes: 1. Faulty correlation of beds at different localities, due largely to failure to take structure into account. 2. Broad use of the term "Notostylopense" so as to include in the one "Formation" beds with dinosaurs + beds with mammals, although they are not in the same bed. 3. Discovery of mammals on or even in the surface of dinosaur bearing beds, + failure to recognize that they were not in place. 4. Identification of crocodile teeth, mammalian laniaries, + perhaps some bone fragments as dinosaurs. [5. Finding of dinosaur bones washed or brought from elsewhere on mammal bearing beds.] Have seen excellent examples of first four. 5 is improbable + was not seen.