364 Trans. Acad. Sci. of St. Louis. 



As a whole the fauna is closely related to that occurring in 

 the Western Hamilton. Some of the species, though bearing 

 different names, are in reality identical with typical forms 

 from that formation. Heretofore, as already stated, the fos- 

 sils have been found, with few exceptions, perhaps, only in the 

 basal portion of what is called the Louisiana limestone, in 

 number 6, a thin sandy layer which is lithologically similar 

 to the partings in the limestone itself. The results of the 

 latest investigations show that many of the forms actually ex- 

 tend upwards, some of them passing practically unchanged 

 through the whole Louisiana to the top of the Hannibal. 

 Thus far not a single species of this fauna appears to occur in 

 the overlying Chouteau. Many of the forms also range down- 

 wards into the dark-colored shale below, which is regarded as 

 of Devonian age, and which a short distance away becomes 

 very much thicker. 



The general impression derived from the table is that the 

 zones 5 to 8 inclusive are faunally very closely related, 

 and that higher ones 9 to 11 also have close affinities with 

 the lower zones. It may be noted in this connection that 

 no special effort was made to determine the full faunas of the 

 hio-her beds, as the critical evidence that was needed was in 

 regard to the fauna of the Louisiana (Lithographic) limestone. 

 The shales have, heretofore, proved to be very barren in 

 organic remains. Towards the top where they become sandy 

 a number of the lower species are found. That the shales do 

 not appear to be fossiliferous is not remarkable. Since they 

 manifestly do not contain abundant remains in a good state of 

 preservation, they have not been searched so carefully by fossil 

 collectors as have the other beds. At Burlington, Iowa, where 

 there are excellent exposures and numerous active local col- 

 lectors, besides a host of transient ones, the same shales re- 

 mained for half a century without a fauna to be ascribed to 

 them. But of late they have been shown to be abundantly 

 supplied with fossils. Without exception the latter appear to 

 be characteristic Devonian forms. As yet, however, the fauna 

 has not been studied sufficiently to be specifically listed, but 

 the brachiopods are for the most part very similar to, if not 

 identical with, the species found in undoubted Devonian shales 



