The next later rocks that have yielded reptilian remains are those of Illinois and Texas formerly supposed to be of Permian age. Later evidence, furnished by invertebrates, however, seems to prove that the lowermost of the strata are of uppermost Carboniferous age. The Illinois deposits, so far as known, are of very limited extent, consisting practically of a single bone-bed in black shale in the immediate valley of the Kaskaskia River near Danville. The known fossils from this bone-bed—all isolated bones—are preserved in the museum of the University of Chicago, and include the types of several genera later recognized in the Texas deposits. The deposits of Texas, extending northward through Oklahoma to the south line of Kansas, are of considerable extent, for the most part lying along the Wichita River and its tributaries, north of Seymour, Texas. They are composed chiefly of red clays and sandstones of fresh-water or delta origin, perhaps eight hundred feet in total thickness. Beds of like character and yielding similar fossils are also known from northern New Mexico on the tributaries of the Chama River. Their chief characters, as well as restorations of some of the more noteworthy forms, have already been given. No vertebrate fossils are known in America from the Upper Permian and Lower Triassic. Marine limestones of Middle and Upper Triassic age of Nevada and northern California have yielded numerous remains of primitive ichthyosaurs, the only known remains of the thalattosaurs, and a few others of doubtful affinities, all of which have been described by Dr. Merriam. The Upper Triassic exposures, of considerable extent, occur between the Pitt River and Squaw Creek in Shasta County, California. Reptilian remains from the Middle Triassic are so far known only from the limestones of West Humboldt and New Pass regions of western and central Nevada. [Illustration: FIG. 29.—Restoration of _Varanops_, a theromorph reptile from the Permian of Texas; about four feet long.]