AMERICAK SPECIES OF OKTHOPHRAGMIKA AND LEPIDOCYCLIKA. 



55 



AMERICAN SPECIES OF LEPIDOCYCLTNA. 



Although numerous species and varieties of 

 orbitoid Foraminifera from many parts of the 

 world have been described, ahnost nothing has 

 been pubhshed on the American species. In 

 1833 Morton ^ described Nummulites man- 

 ieUi, which was later taken by Gumbel in 1868 

 as the type of a subgenus of Orbitoides that he 

 named Lepidocydina. This is now recognized 

 as a genus, and L. manteUi (Morton) is the 

 type species. In 1865 Conrad ^ pubhshed a 

 brief description of Orbitolites supera, which 

 may now be known as Lejndocyclina supera 

 (Conrad). These are the only species of or- 

 bitoid Foraminifera from the Coastal Plain 

 region of the United States of which descrip- 

 tions had been published prior to the pubhca- 

 tion of my paper on orbitoid Foraminifera of 

 the genus OrthopTiragmina from Georgia and 

 Florida,^ in 1917. Two species of Lepido- 

 cyclina from Panama (i. caneUei and L. cha- 

 eri) were described by Lemoine and R. 

 Douville * in 1904, and H. Douville ^ has re- 

 cently described two species from Trinidad 

 {L. pustulosa and L. tohleri). 



Several works refer to American species 

 under names which were erroneously applied 

 to them, but most of these species do not even 

 belong to the genus Lepidocydina. 



From the collections of the United States 

 Geological Survey, especially those obtained 

 by T. Wayland Vaughan and C. Wythe Cooke, 

 there has been placed in my hands a mass of 

 material representing the Eocene and Oligo- 

 cene deposits of the Atlantic and GuH Coastal 

 Plain of the United States. In addition I 

 have examined collections from Panama ob- 

 tained by Mr. Vaughan and the geologist of the 

 Panama Canal Commission, Donald F. Mac- 

 Donald; from Antigua and St. Bartholomew, 

 by Mr. Vaughan; from Cuba, by Messrs. 

 Vaughan, Darton, Hayes, Spencer, and Mein- 

 zer; and from Mexico, by E. T. Dumble, 

 geologist for the Southern Pacific Railroad. 

 These collections, with miscellaneous lots from 

 many other localities, contain a great many 

 specimens of Lepidocydina and are repre- 

 sentative of many regions. 



1 Am. Jour. Sci., vol. 23, p. 291, pi. 5, fig. 9, 1833. 



2 Acad. Nat. Sci. Philadelphia Proc, No. 2, p. 74, 1865. 



3 Cushman, J. A., U. S. Geol. Survey Prof.Paper 108, pp. 115-124, pis. 

 40-44, 1917. 



* See. g^ol. France, Pal^ontologie, Mdm. 32, 1904. 

 » Compt. Rend., 1917, pp. 843, 844, .figs. 1-6. 



A study of the collections shows that this 

 general region contains a few widely dis- 

 tributed species which have already been found 

 elsewhere, but by far the largest number of the 

 species are undescribed, although some of 

 them show relationships with species from 

 other areas. 



As a rule the species seem to have a very 

 short vertical range and may therefore be 

 used as index fossils for those formations in 

 which they occur. The stratigraphy of the 

 Coastal Plain region is now well coordinated, 

 and it is possible to place the species very 

 definitely, but in many other regions the de- 

 tailed stratigraphy is not fully known, and 

 comparisons are more difficult. 



It is evident that in America Lepidocydina 

 is found both in the upper Eocene and in the 

 lower and middle Oligocene as now under- 

 stood. The detailed structure and the bio- 

 ogic relations of the various species are inter- 

 esting but are reserved for discussion in a future 

 paper. 



In general the habitat in which Lepidocydina 

 was first developed was in fairly quiet waters 

 of a tropical temperatm-e and probably at 

 depths less than 25 fathoms. The associated 

 genera, Operculina, Heterostegina, Oarpenteria, 

 and Gypsina, are, so far as their livmg repre- 

 sentatives show, characteristic of such con- 

 ditions. 



As an aid in understanding the structiu-e of 

 Le pidocydina ior one not used to the terminol- 

 ogy the accompanying diagrammatic figure of 

 a vertical section has been introduced. The 

 structure involves two distinct masses of cal- 

 careous material — that belonging to or origi- 

 nating from the median layer (stippled in the 

 figm-e) and that belonging to the lateral layers 

 (solid black in the figure). In the central re- 

 gion are the embryonic chambers, one or more, 

 in the megalospheric form of any species 

 usually large and rounded. Surrounding these, 

 usually in a single plane, are numerous equato- 

 rial chambers, shown in the diagram as two 

 series on opposite sides of the embryonic cham- 

 bers increasing in height from the center toward 

 the periphery. Above and below this band of 

 equatorial chamb'ers, and usually covering them 

 except near the periphery, are the numerous 

 lateral chambers, usually seen in vertical sec- 

 tion piled one above another in vertical col- 



