THE FORAMINIFERA OF THE BYRAM CALCAREOUS MARL AT BYRAM, 



MISSISSIPPL 



By Joseph A. Cushman. 



INTRODUCTION. 



The lovvei' Oligocene of the southeastern 

 Coastal Plain of the United States is in Missis- 

 sippi divisible into several distinct members. 

 Farther east these divisions are not so clearly 

 distinguishable. Of the divisions in Missis- 

 sippi the Byram calcareous marl is the young- 

 est. The type section for the Byram marl is 

 an exposure at the bridge over Pearl River 

 at Byi-am, Hinds County, Miss. The forma- 

 tion is mainly a sandy glauconitic marl with 

 thin beds of impure limestone, clay and sand. 



Small lots of the marl from the type section, 

 United States Geological Survey station 6455, 

 collected by E. N. Lowe in 1912, were examined 

 after careful washing. Although but a few 

 cubic centimeters of the original material was 

 taken it has given 68 species and varieties of 

 Foraminifera. More species will probably be 

 added by a further search of the material, but 

 it is probable that all the common species are 

 described in this paper. An examination of 

 the Byram marl from other localities will 

 undoubtedly greatly increase the fauna, but 

 it is very desirable in close stratigraphic 

 studies to have the type section very delinitely 

 worked up for comparison with sections in 

 other areas, and in this paper it has been the 

 aim to furnish data for such comparisons. 



RELATIONSHIPS OF THE BYRAM FAUNA. 



Of the 6S species and varieties which are 

 here recorded from the type section of the 

 Byram calcareous marl, 28 appear to have 

 been previously undescribed, and 8 of these are 

 recorded under the genus only, as the available 

 material was not abundant enough to warrant 

 specific determination. This statement may 

 be compared with the data given in the 

 accompanying paper by Cooke, who lists 134 

 species of mollusks, 5 corals, and 2 ecliino- 

 dernis, 54 of which are peculiar to the marl at 

 Byram. 



One of the most interesting features dis- 

 closed in the study of the Foraminifera of this 

 collection has been their relationships with 

 other faunas. The different species are very 

 definitely related both to the fossil Foramini- 

 fera so far known from the Atlantic and Gulf 

 Coastal Plain of the United States and to the 

 living Foraminifera of certain regions, espe- 

 cially the Indo-Pacific. 



By far the larger proportion of the species 

 and varieties are identical with or closely 

 related to species now living in the Indo- 

 Pacific. Such species as Textularia folium 

 Parker and Jones, Bolivina amygdalacformw 

 H. B. Brady, Bolivina nitida H. B, Brady, and 

 Hanerina fragilissima H. B, Brady are now 

 living in the Indo-Pacific region but are not 

 recorded elsewhere nor have they been pre- 

 viously recognized in the fossil form. They 

 show rather conclusively that there is a very 

 close relationship between the fossil fauna at 

 Byram and the living fauna of the Indo-Pacific. 



Of the species here described as new there 

 are several that are also clearly related to the 

 living Indo-Pacific fauna. For example, Bis- 

 corbis hyramensis Cushman, n. sp., is nearest 

 in its affinities to D. corrugata Millett, described 

 from specimens collected in the Malay Archi- 

 pelago and recorded by Heron-Allen and Ear- 

 land from the Kerimba Archipelago, off the 

 southeastern coast of Africa, from the coast of 

 Burma, and from West Australia, thus having 

 a wide Indo-Pacific range. In the characters 

 of its ventral surface D. hyramensis Cushman is 

 also related to D. pafelliformis II. B. Brady and 

 D. fahernacularis H. B. Brady, both typical 

 Indo-Pacific species. The Byi-am species is 

 then a fossil representative of a small well- 

 distinguished group of species, the others of 

 which are now living in the Indo-Pacific. 



PolyinorpMna regina H. B. Brady, Parker, and 

 Jones also shows a definite faunal relation. As 

 a recent species it is known from the shallow 



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