INTRODUCTORY REMARKS. 25 



earlier forms of the Mauvaises Terres of White River, and on the other hand with still later or recent 

 forms. The collection sent to the Smithsonian Institution was thence transmitted to the author, and is 

 noticed in the Proceedings of the Academy for 1858. It also forms a most important portion of the 

 material of the present work. 



As a further contribution to the latter, additional material was obtained by Dr. Hayden, who made 

 another expedition in the summer of 1866 to the Mauvaises Terres of White River, under the auspices 

 of this Academy. 



The Mauvaises Terres fossils are thoroughly petrified, their original peculiar animal matters being 

 almost entirely replaced by ordinary mineral matter. 



The bones are usually white or cream-colored, yellowish-white, and more rarely iron-gray. They 

 are hard, compact and heavy ; brittle, but rarely friable. The interior spongy substance, vascular 

 canals, and generally the medullary cavities are occupied with dense mineral matter, usually silex in 

 the form of chalcedony, which in the larger medullary cavities, partially occupied, has a botryoidal 

 arrangement. 



The bones are preserved in various degrees of integrity, many being nearly perfect, but generally 

 the skulls are more or less fissured or otherwise fractured, and some are more or less crushed. Not- 

 withstanding their fractured condition, usually the fragments are retained in their original relative 

 position by the associated matrix, which occupied all the cavities and depressions of the fossils, and in 

 many instances more or less enveloped the specimens. 



The fossils exhibit the appearance of having been originally imbedded in soft mud, and subsequently 

 submitted to more or less pressure, which will account for their fissured appearance without any great 

 extent of displacement of the fragments. 



The teeth are generally in a perfect state of preservation. Their dentine is white or cream-colored, 

 and compact, though more friable than in the recent condition. The enamel is well jareserved in 

 texture, but is invariably stained. Its color varies in different specimens, from a light translucent 

 brown with a corneous aspect, passing through different shades of brown to grayish and bluish-black. 

 Its surface is highly lustrous, and when dark in color looks in some instances like polished iron. 



None of the fossils have the appearance of being water-worn or rolled, but all the bones and teeth 

 are preserved with their original freshness of shape and sharpness of detail. The condition of the 

 specimens indicates the carcasses of the animals to which the bones belonged to have undergone 

 decomposition in comparatively quiet water, on a soft muddy bed, which is further proved by the 

 character of the associated matrix of the fossils. 



The matrix, slightly variable in character from the different strata, is usually of a dull grapsh, or 

 whitish ash, or dusky cream color, sometimes with a pinkish aspect, homogeneous, and without 

 admixture of pebbles or visible sand. It is harder than ordinary chalk, but softer than marble or 

 ordinary limestones, is not crystalline, nor does it exhibit distinct lines of stratification. It is mainly 

 composed of silica with carbonate of lime, or, in other words, it is a soft siliceous limestone. 



It is a remarkable circumstance that among the large quantity of fossil bones brought from the 

 Mauvaises Terres and submitted to the examination of the author, certainly amounting to several tons 

 in weight, there were detected no trace of remains of birds or fishes, and the same may be said of 

 reptiles, except one species of turtle. The remains of the latter are exceedingly numerous, consisting 

 almost exclusively of the shells, or carapace and sternum, filled with matrix occasionally envelojjing 

 some of the bones of the interior skeleton. The fossil turtles were so abundantly strewed over the 

 country of some parts of the Mauvaises Terres, that localities have been named after them. 



The fossil turtle shells of the Mauvaises Terres exhibit considerable variety of form, varying in the 



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