466 Trans. Aead. Set. of St. Louia. 



cent of the species recognized occur also in the Glen Park 

 fauna, none of the remaining forms being identified specific- 

 ally. Several of the unidentified forms are certainly unde- 

 scribed species, some are members of genera represented in 

 the Glen Park fauna by undetermined species, and in a few 

 instances may prove to be identical with Glen Park species, 

 in which case the percentage of identical species in the two 

 faunas will be increased. Notwithstanding the strong simi- 

 larity between the Hamburg and Glen Park faunas, the 

 dominant species in the two localities are quite different, the 

 most common members of the Glen Park fauna being: absent 

 from Hamburg, and the most common Hamburg species being 

 absent from Glen Park. Furthermore the species common to 

 the two localities are usually represented by larger individuals 

 at Hamburg than at Glen Park. 



The presence of this fauna at Glen Park and Hamburg may 

 not have been strictly contemporaneous, but its occurrence at 

 the two localities is without doubt associated with the same 

 wave of migration and the fauna at the two localities may be 

 considered to be synchronous within comparatively narrow 

 limits. 



The gtratigraphic position of the fauna at Hamburg in re- 

 lation to the Louisiana limestone fauna is of prime import- 

 ance in determining the true relations of all the Kinder- 

 hook beds of south-eastern Missouri. In its typical expres- 

 sion in Pike County, Missouri, the Louisiana limestone at- 

 tains a thickness of from fifty to sixty feet, the known 

 fauna being restricted to a few feet at the base of the 

 formation. At Hamburg the same formation in its typ- 

 ical expression is only four or five feet in thickness, the 

 fauna being essentially identical in all respects with that of 

 the lower few feet of the formation at Louisiana, Missouri. 

 Beds No. 8 aud No. 9 of the Hamburg section are apparently 

 a continuation of the Hannibal shales and sandstones of the 

 Louisiana section, so that beds 5, 6 and 7 of the Hamburg 

 section may be included with bed 4, as the essential time 

 equivalent of the whole Louisiana limestone. 



If this interpretation is correct, the time during which the 



