14 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 76 



Toward the equatorial layer the chamber roofs are so thickened as 

 almost to obliterate the chamber cavities; near the surface the roofs 

 are thinner, 23m to 30^ thick, and the cavities are more open, but 

 they are not of uniform thickness. The chamber lengths are also 

 very variable, ranging from 40yu or less to as much as 250/u. Pillars 

 are well developed. Some have their origin at the equatorial layer 

 and extend as narrow cones to the outer surface, where they form, 

 papillae as much as 160m thick. 



Locality and geologic horizon. — About 2 miles south of Zaragosa, 

 State of Nuevo Leon, Mexico (collected by T. W. Vaughan, Novem- 

 ber 7, 1920), in association with Venericardia potapacoensis Clark 

 and Martin. The horizon is very low in the Claiborne group or 

 high in the Wilcox group; that is, very low middle or very high 

 lower Eocene. 



Cotypes.— Cat. No. 371010, U.S.N. M. 



Discocyclina zaragosensis differs so much from any other hitherto 

 described American species that it scarcely needs to be compared 

 with any of them. The most nearly related species is probably D. 

 perTcinsi Vaughan from the upper Eocene of Jamaica, but that species 

 is larger, not so distinctly domed in the center, and its papillae are 

 finer. 



DISCOCYCUNA CLOPTONI, new species 



Plate 5, figures 1-6 



1925. Orthophragmina species Vaughan, Second Pan-Pacific Sci. Cong. 

 (Australia) Proc, vol. 1, p. 870. 



Test very thin, lenticular, nearly flat or slightly undulate. Diam- 

 eter ranges from 6.5 to 10 mm.; outer faces almost parallel; thick- 

 ness through the center of a specimen about 8 mm. in diameter 

 about 425m, (pl- 5, fig. 6). Surface beset with very minute papillae, 

 50m, or even less, thick. 



Embryonic apparatus composed of two, four, six, or eight chambers. 

 In specimens in which it is composed of two chambers, it is typically 

 reniform, 350m across the chambers between the horns of the outer 

 chamber and 300m perpendicular to that line through the center of 

 the initial chamber. The walls are rather thick, about SOm- There 

 may be two, three, or four such pairs of chambers, as is shown in the 

 illustration (pl. 5, figs. 2, 3, 4, 5). 



Equatorial chambers rectangular, arranged in definite annuli, which 

 increase in width toward the periphery of the test. About 2 mm. 

 from the center of the specimen illustrated by plate 5, figure 2, the 

 width of an annulus is from about 40m to 60m. In another specimen 

 the width near the center is about 24m, but at the periphery it is as 

 much as 100m; about 80m is frequent. The radial walls are not well 



