DEVONIAN AND MISSISSIPPIAN FAUNAS 109 



bed beneath the Hmestone. In southeastern Missouri a one-foot bed 

 of sandstone occurs at the base of the Kinderhook with numerous 

 phosphatic nodules and some worn Ptyctodus teeth. In southwestern 

 Missouri a thin formation at the base of the Kinderhook has been 

 described by Shepard' as the Phelps sandstone, in which Ptyctodus 

 teeth are abundant, and the same conditions obtain at Providence,^ 

 in central Missouri. In all of these localities the same species, Ptyc- 

 todus calceolus N. and W., seems to be the usual form. Occupying, as 

 these Ptyctodus beds do, a position immediately superjacent to a more 

 or less profound unconformity, it is not likely that it is strictly contem- 

 poraneous in all of these localities, but that they are all associated 

 with one general geologic movement, and are contemporaneous within 

 comparatively narrow limits, is quite certain. The presence of the 

 remains of this fish fauna, in both the southern and northern Kinder- 

 hook provinces, while the invertebrate faunas are so distinct, is doubt- 

 less due to the fact of the greater mobility of the fishes, and their 

 greater powers of adaptation to certain changing conditions. 

 Besides these fish remains, the most common fossil in the Sweetland 

 Creek beds is a crustacean belonging to the genus Spathiocaris, which 

 also occurs in the Upper Devonian black shale in southern Indiana 

 and Illinois, and in a basal Kinderhook shale in southwestern Mis- 

 souri. This crustacean, like some of the Lingulas, seems to be associ- 

 ated rather with a peculiar type of sediment than with a definite time 

 period of narrow limits. Neither the Ptyctodus nor the Spathiocaris 

 have been found in the basal Kinderhook shales at Burlington, but the 

 fauna of the basal portion of the formation is of course not known. 



During the progress of Kinderhook time the sea was encroaching 

 from both the north and the south, until before the close of the epoch 

 free communication was established between the earlier separated 

 provinces and the fauna of the southern province became the dominant 

 type throughout the entire Mississippi Valley Basin. This northern 

 incursion of the southern fauna is well exhibited in the uppermost 15 

 feet of the Kinderhook section at Burlington and elsewhere. 



From the outline of the faunal history here given, it is evident that 

 the arrangement of the Kinderhook formations into three successive 



1 Mo. Geol. Surv., XII, 77. 



2 "Bed No. 4, Stewart," Kansas Univ. Quart., IV, 161. 



