44 THE DEVONIAN OF MISSOURI. 



Pelecypoda. — Pelecypods are abundant near the top of the 

 formation, especially in the Cow Creek locality. Paracyclas 

 elliptica Hall is the most abundant form. Modiomorpha mis- 

 souriensis Branson and Schizodus chemungensis (Conrad) are 

 also abundant. Goniophora hamiltonensis (Hall) is a significant 

 form, though rare, on account of its occurrence in the Hamilton 

 and Upper Devonian of the eastern part of the United States 

 and Canada. 



Below the upper fifteen feet of the formation pelecypods 

 are rare. 



Gastropoda. — Diaphorostoma snyderensis Branson is the 

 only abundant gastropod and it is abundant in only two mem- 

 bers of the lower half of the formation. Pleurotomaria isaacsi 

 Hall and Whitfield is significant on account of its occurrence 

 in both the Snyder Creek and Lime Creek formations. 



Cephalopoda. — The cephalopods are too poorly preserved 

 and rare to be a significant element in the funa. 



Trilobita. — Only one specimen of trilobite, a pygidium, has 

 been collected, and its identification is uncertain. 



Pisces. — Fishes are generally rare. Ptyctodus calceolus 

 Newberry and Worthen is a common form which ranges from 

 Mineola to basal Mississippian in Missouri. Only two speci- 

 mens of Ptyctodus ferox Eastman have been collected. Glyptaspis 

 is too fragmentary to be identified specifically and only one 

 specimen has been collected. Fragments of three or four other 

 species of dinichthyids have been collected. 



Correlation. — The Snyder Creek faunas indicate a more or 

 less isolated sea during most of the epoch. One of the closest 

 relationships of the fauna is with the Lime Creek faunas of 

 Iowa. Fenton 1 lists about 100 identified species from the Lime 

 Creek and only 12 of these occur in the Snyder Creek. 53 

 species have been identified from the Snyder Creek and 12 of 

 these occur in the Lime Creek. 



Lioclema occidens (Hall and Whitfield) and Stromaiopora 

 solidula Hall and Whitfield form the closest tie between the Lime 

 Creek and Snyder Creek as both are abundant forms that oc- 

 cur in no other formations. Chonophyllum ellipticum Hall and 

 Whitfield also is confined to the two formations. 



The following is a complete list of the species common to 

 the two formations: 



'Am, Midland Naturalist, vol. 6, pp. 188-197. 



