56 



SHORTER OOTiTTRIBUTIONS TO GENERAL GEOLOGY, 1919. 



umns. In many species pillars are developed, 

 usually solid masses of calcareous material origi- 

 nating at the wall of the horizontal series and 

 extending to or toward the surface of the test. 

 These pillars in some species rise above the sur- 

 face and form the pustules or papiUae of the 

 surface ornamentation. 



A horizontal section such as shown in Plate 

 XXIX, figure 3, is made at right angles to 

 that shown in the diagram and ])asses through 

 the plane of the equatorial chambers. Such 

 a section shows that the equatorial chambers 

 in this genus have typically a hexagonal form, 

 although this may often be modified to an 

 ogival form or in certain species even to the 



Undoubtedly other species wlU })e found 

 when more geologic work is done in the different 

 areas, and probably more careful detailed 

 collecting will show that special varietal 

 forms of the various species occur at difTcrent 

 horizons. Most of the species represented 

 in the collections now available are here de- 

 scribed, so that the information thus far 

 obtained may be used as a basis for further 

 work and in helping to solve problems of 

 stratigraphic correlation. It is hoped that 

 this ])a2)er may be followed by a ])aper giving 

 some of the interesting facts of structure and 

 biologic relations that are shown by the species 

 of this genus. 



Figure 3.— Diagrammatic vertical section of Lepidocyclina. Material of the wall of the embryonic chambers (the two large ones in the center), 

 of the equatorial chambers (the two central bands passing to right and left), and the pillars in light stipple. Walls of the lateral chambers 

 in solid black. Areas of the chamber spaces white. 



rhc)ml)oid. Thus a horizontal section wiU 

 discriminate this genus from the other orbitoid 

 genus, Ortlioi)liragmLna, with which it occurs, 

 as in Orthophragmina the equatorial chambers 

 are elongate and rectangular. 



Of the Coastal Plain species the following 

 seem to be characteristic of certain formations: 



Chattahoochee formation (middle Oligocene): 



L. chattahoochoensis. 

 Byram calcareous marl (lower Oligocene): 



L. supera. 

 Marianna limestone (lower Oligocene): 



L. mantelli. 

 Ocala limestone (upper Eocene): 

 Especially in Florida: 

 L. ocalana. 



L. ocalana var. subdecorata. 

 L. floridana. 

 L. pseudocarinata. 

 L. paeudomarginata. 

 Ij. attenuata. 

 L. fragili.s. 

 L. cookei. 

 Especially in Georgia: 

 L. georgiana. 

 Jackson formation (upper Eocene): 

 Especially in Louisiana: 

 L. mortoni. 



By means of the subjoined key it may be 

 possible to identify American material that is 

 sufTiciently well preserved. 



Key to the American species of Lepidocyclina. 



Test of two distinct portions, a central thickened portion 

 and a very thin peripheral portion : 

 Central portion deeply pitted : 



Pits few and large, test strongly sellaeform, 



diameter 15 to 18 millimeters L. favosa. 



Pits numerous and small, test slightly sellaeform, 

 diameter 15 to 25 millimeters. 



L. chattahoocheensis. 



Central portion smooth L. pseudocarinata. 



Central portion papillate: 



Papillae fine, central area small. .L. attenuata. 



Papillae coarse, central area large L. cookei. 



Test comparatively thin with small central umbo: 



Test of medium size, flat, diameter 20 to 35 millimeters: 



Surface smooth L. mantelli 



Surface papillate L. hilli. 



Test large, diameter 50 to 100 millimeters: 



Umbo small, surface slightly papillate, lateral 

 chambers few, only 6 in a vertical column 



pillars small and scattered L. undulata. 



Umbo prominent: 



Surface papillate, pillars numerous, lateral 

 chambers 20 or more in a vertical column 

 L. georgiana. 



