490 PROCEEDINGS OF THE NATIONAL, MUSEUM vol. Sn 



In a specimen 2.3 mm in diameter the final chamber has a height 

 of 0.5 mm. 



The sutures are thin and radiate nearly straight from the center 

 until near their proximal ends, where they recurve sharply. The 

 curvature is such that the peripheral end of a suture nearly touches 

 the adjacent one. 



Cotypes.—U.S.'NM. no. 495189. 



Localities. — At the base of the bluff on the Rio Pantcpec 2.2 km 

 south, 20° west, from the Buena Vista Hacienda House, Canton 

 Metlaltoyuca, State of Pueblo (M 71 V) ; cotypes, Rio Yinazco, 

 right bank, 1.4 km (M 80 V) and 1.35 km (M 81 V) downstream 

 from the road crossing from Buena Vista to Vinazco, Canton Chi- 

 contepec, State of Veracruz. Collected by T. Wayland Vaughan for 

 the Aguila Co. 



Geologic lioHzon. — Upper Eocene, stratigraphic equivalent of the 

 Tantoyuca formation. Associated with LepidocycUna tohleri H. 

 Douville, L. tinnitatis H. Douville, and L. niacdoncddi Cushman. 



OPERCULINOIDES VICKSBURGENSIS, new species 

 Pr>.\TE 36 



Nummulites sp. Cushman, U. S. Geol. Surv. Prof. Pap. 129-E, pp. 100-101, 



pi. 24, fig. 4, 1922. 

 Nummulites sp. Vaughan, Geol. Soc. Amer. Bull., vol. 35, p. 787, 1924. 



Test rather small, involute, compressed lenticular, outer surface 

 without ornamentation except the traces of flexuous septal markings 

 and a small area of clear shell material in the center from which 

 the septa radiate. The test is nearly circular; the diameter from 

 outer edge of aperture through center ranges from 1.3 to 3.1 mm; 

 diameter at right angles to line through aperture ranges from 1.2 

 to 3 mm; thickness through center ranges from 0.3 to 0.6 mm. 

 From the central area the test slopes very gradually to the bluntly 

 rounded periphery. 



An accidental median section of a specimen (pi. 36, fig. 2) 2.1 mm 

 in diameter shows 3^^ coils, with 18 chambers in the last coil. A 

 thin section of a specimen (pi. 36, fig. 4) 2.5 mm in diameter has 

 22 chambers in the final volution; another section (pi. 36, fig. 5) 

 has 4 coils and 25 chambers in the last coil. An uncut specimen 

 2.2 mm in diameter has 22 chambers showing at the surface, while 

 another 2.8 mm in diameter has 26 chambers. 



The sutures are moderately thick and radiate from the center 

 with only slight curvature until near the periphery, where they bend 

 backward evenly but sharply. There is a slight but regular increase 

 in height of the chambers. The initial chamber is circular, about 

 COfj. in diameter. 



