NO. 2023. A BRACKISH WATER PLIOCENE FAUNA— DALE. 227 



and explored for fossils by Messrs. Vaughan and Matson, These 

 were, respectively, 1 (station 3614) and 3 (station 6440) miles southeast 

 of Burkeville. The material here is a fragmentary rock, with very 

 poorly preserved fossUs, almost all in the form of molds or internal 

 casts, and contains, besides traces of barnacle valves and mollusks, 

 bones of birds and carbonized fragments of wood. The molluscan 

 fauna is mostly the same as at the Satilla locality. 



Mr. Geo. C. Matson has kindly furnished the following data in 

 regard to the geological conditions at Burkeville: 



My collection was obtained from the south side of Cow Creek about one to one 

 and a half miles from the town of Burkeville, Texas. The fossils occurred as casts 

 and molds in lenses of limestone about four to six inches thick. These lenses are 

 exposed in a small gully and the available area for collection does not exceed four or 

 five square feet. 



The limestone is very hard and weathers light gray or yellow with a rough sur- 

 face resulting from unequal resistance to solution. Associated with the imprints of 

 shells are a few fragments of bones, but it is difficult to obtain anything but frag- 

 ments of either vertebrate or invertebrate remains because the rock splits so irregu- 

 larly. The limestone lenses are imbedded in a very plastic clay which is light blue 

 or green where recently exposed but changes to black or brown on weathered sur- 

 faces. In this clay or scattered over its surface are many rounded or oval concre- 

 tions of calcium carbonate, occasional vertebrae and fragments of other bones, together 

 with oyster shells similar to those found in the limestone. The concretions vary 

 from small nodules, apparently formed by the cementing of still smaller granules, 

 to flat bowlders from a few inches to a foot or more in diameter. Many of the larger 

 concretions show concentric and radial cracks filled with calcite and are therefore to 

 be classed as septaria. 



The black clay found at this locality is not confined to the vicinity of Burkeville, 

 for it extends southward about four miles and is reported some distance north of town. 

 This clay may be traced into western Louisiana where it forms the Anacoco prairies. 

 By means of scattered outcrops it is possible to determine its occurrence several 

 miles east of the Texas-Louisiana boundary. 



The interest of this fauna lies not only in its being strictly brackish 

 water and containing a large number of hitherto unknown species, 

 but in its wide distribution along the edge of the PHocene coastal 

 plam, forming a faunal horizon hitherto unrecognized. 



The conditions appear to have been not unlike those which obtain 

 at certam portions of the Gulf coast to-day; probably lagoons into 

 which the streams poured fresh water carrying with it small fresh- 

 water gastropods and occasionally valves of Unionidse. On the other 

 hand, the sea had access to the lagoons, keeping the salinity of the 

 water such that oysters and anomias could flourish with other smaller 

 mollusks which frequent oyster beds, while occasionally purely salt- 

 water shells might be ejected by wandering fishes or carried by 

 violent storms. 



It will be noted that the softer marl of Satilla River has preserved 

 most of the small fresh-water gastropods, which are absent from the 

 coarser sediments of the western localities where the oysters appear 



