NO. II FORAMINIFERA OF VENEZUELA GRAVELL 3I 



Lepidocyclina {Nephrolcpidina) undosa is a very common and 

 widely distributed middle Oligocene species. Besides Venezuela, it 

 occurs at numerous localities in Mexico, Antigua, Jamaica, and 

 Trinidad. Gorter and Van der Vlerk (25, p. no) place L. undosa 

 in the subgenus Nephrolepidina. A large number of sections of this 

 species show the embryonic apparatus varying from the nephro- 

 lepidine to eulepidine type, making the assignment of this species to 

 either subgenus virtually optional. 



LEPIDOCYCLINA (NEPHROLEPIDINA) sp. 



Plate 5, figs. 9, 10; plate 6, fig. i 



Thin sections of hard San Luis limestone from locality 1209 contain 

 a few rather poorly preserved specimens of Nephrolepidina, associated 

 with a few specimens of Gypsina glohidus (Reuss), a few specimens 

 of a small indeterminate species of Camerina, several genera of small 

 foraminifera, and calcareous algae. 



Test variable in shape ; some specimens have a large centrally 

 thickened area, well demarked from a surrounding rim, in others the 

 thickness of the test decreases gradually from the center to the 

 periphery. Some of the specimens are strongly curved, whereas 

 others show little or no curvature. 



A megalospheric specimen, which has its edges broken, is 12 mm in 

 diameter. It is possible that the megalospheric form attains a diameter 

 of 20 mm ; thickness through center up to about 2 mm. . 



Embryonic apparatus of Nephrolepidina type, composed of an 

 initial ovate chamber about 360 /a long and about 260 jx wide, half 

 surrounded by a crescent-shaped chamber about 200 by 530 /a. Both 

 chambers are enveloped in a common wall about 50 /x thick ; height 

 about 500 /;t. 



Equatorial chambers hexagonal in horizontal section ; radial and 

 tangential diameters about 70 ju.. The equatorial layer increases but 

 slowly in height toward the periphery ; height about 80 /t near the 

 embryonic apparatus ; about 120 /* high at a distance of 1.6 mm from 

 the embryonic apparatus; roofs about 15 /* thick. 



Lateral chambers low and flat, about 15 layers over the center of 

 the test in a tier 660 fx high, or about one chamber to 44 /a ; chamber 

 spaces about 30 /x high; roofs about 15 /i. thick; length increases 

 from about 60 /a at the equatorial layer to about 200 /a at the surface 

 of the test. The number of layers of lateral chambers decreases from 

 15 over the center to one or two layers at the periphery. The pillars 

 are small, regular in distribution, originating at the equatorial layer 

 3 



