313] G. E. Dorsey 115 



deposit than the Selma or the Eipley to the west. Through- 

 out the Ripley in Georgia are found remains of plants and 

 lignite, clearly pointing to an estuarine or very near-shore 

 origin. On the other hand, Professor E. W. Berry has in- 

 formed me that to his knowledge there has never been a 

 piece of lignite found in the Chalk. The grading of the 

 Chalk, to the east, into sands and muds, is thus to be taken 

 as indicating an approach to land, and hence to compara- 

 tively muddy waters, which we shall see were intolerable sur- 

 roundings for this species. 



This list of occurrences exhausts the localities for B. ameri- 

 cana. It is restricted to the Atlantic and Eastern Gulf pro- 

 vinces of the United States, occurring at the Monmouth or 

 Exogyra costata level of the Upper Cretaceous along the At- 

 lantic coast and in the eastern part of the Mississippi Embay- 

 ment. The generalization that B. americana occurs mainly in 

 a chalky or a glauconitic-greensand facies will be seen to hold 

 true to a remarkable extent throughout this range. Although 

 absent in many instances in favorable lithology, I have yet 

 to discover an occurrence in a facies radically different from 

 the above. 



The European occurrences of the form, known as Belemni- 

 tella mucronata, D'Orbigny, conform in every way to the re- 

 strictions in lithologic characteristics imposed by B. ameri- 

 cana. As noted elsewhere, the European horizons at which 

 B. mucronata occurs are slightly younger than the American. 

 We first observe its presence in the uppermost Campanian, 

 but it is the Maestrichtian that witnesses its widespread dis- 

 tribution. A glance at a map (e. g., Haug, 13, p. 1299) 

 showing the distribution of the various Neocretaceous de- 

 posits will show that the occurrence of chalk is, broadly, in 

 a northwest-southeast belt, from Antrim in Ireland, across 

 England, into Germany and Poland, and along the eastern 

 front of the Carpathian Mountains, with large areas in cen- 

 tral and eastern Eussia, and the Caucasus and Trans-Cau- 

 casus. Southwest from this main basin, from Sweden through 

 eastern France, is a subordinate trough, with a few isolated 



