_Triassic Mammifer (Microlestes antiquus Plieninger.)_--In the year 1847, Professor Plieninger, of Stuttgart, published a description of two fossil molar teeth, referred by him to a warm-blooded quadruped[xiii-A], which he obtained from a bone-breccia in Wuertemberg occurring between the lias and the keuper. As the announcement of so novel a fact has never met with the attention it deserved, we are indebted to Dr. Jaeger, of Stuttgart, for having recently reminded us of it in his Memoir on the Fossil Mammalia of Wuertemberg.[xiii-B] Fig. 529. represents the tooth first found, taken from the plate published in 1847, by Professor Plieninger; and fig. 530. is a drawing of the same executed from the original by Mr. Hermann von Meyer, which he has been kind enough to send me. Fig. 529. is a second and larger molar, copied from Dr. Jaeger's plate lxxi., fig. 15. [Illustration: Fig. 529. _Microlestes antiquus_, Plieninger. Molar tooth magnified. Upper Trias, Diegerloch, near Stuttgart, Wuertemberg. _a._ View of inner side? _b._ same, outer side? _c._ Same in profile. _d._ Crown of same.] [Illustration: Fig. 530. _Microlestes antiquus_, Plien. View of same molar as No. 529. From a drawing by Herman von Meyer. _a._ View of inner side? _b._ Crown of same.] [Illustration: Fig. 531. Molar of _Microlestes_? Plien. 4 times as large as fig. 529. From the trias of Diegerloch, Stuttgart.] Professor Plieninger inferred in 1847, from the double fangs of this tooth and their unequal size, and from the form and number of the protuberances or cusps on the flat crowns, that it was the molar of a Mammifer; and considering it as predaceous, probably insectivorous, he called it Microlestes, from +mikros+, little, and +lestes+, a beast of prey. Soon afterwards, he found the second tooth also, at the same locality, Diegerloch, about two miles to the south-east of Stuttgart. Some of its cusps are broken, but there seem to have been six of them originally. From its agreement in general characters, it is supposed by Professor Plieninger to be referable to the same animal, but as it is four times as big, it may perhaps have belonged to another allied species. This molar is attached to the matrix consisting of sandstone, whereas the tooth, No. 529., is isolated. Several fragments of bone, differing in structure from that of the associated saurians and fish, and believed to be mammiferous, were imbedded near them in the same rock.