SPECIES OF CAMERINIDAE — BARKER 311 



test than is shown in the figures of Rutten or Rutten and Vermunt. 

 The latter authors place O. afascaderensis Berry and 0. peruviana 

 in the synonymy of 0. nummulitifoimiis^ with which I am in agree- 

 ment. Thus we have a wide-ranging form occurring in the upper 

 Eocene of Peru, Ecuador, Curasao, alid Mexico. 



PJesiotyjyes.—U.^.'^M. no. 497834. 



Other specimens.— U.S. ^M. no. 497833. 



Occitrrence (in Mexico). — Tantoyuca formation, Jackson Eocene. 



OPERCULINOIDES PRENUMMULITIFORMIS, new species 



Plate 12, Figures 1, 2 ; Plate 17, Figuke 4 ; Plate 21, Figure 2 



Test of medium size, very compressed, completely involute, the last 

 whorl somewhat thinner than the earlier coils. Sutures are slightly 

 raised, rather limbate, and show a tendency to become beaded, 

 especially toward the center of the test. Diameter, up to 4.0 mm, 

 average 3.25 mm; average thickness, 0.5 mm. 



Sections show the test to be composed of 314 to nearly 4 whorls, 

 with 22 to 27 chambers in the final whorl. The septa are numerous, 

 thin, and uniformly curved throughout their length. The chambers 

 are long and narrow and of even size and shape, in contrast to the 

 irregularities shown by the closely allied form O. nummulitiformis 

 (Rutten). Sections also reveal the presence of numerous supple- 

 mentary or secondary apertures, irregularly distributed along the 

 septa as illustrated by Carpenter ("secondary pores," 1862, p. 254, 

 fig. 12). The exact significance of these has not yet been satisfac- 

 torily explained, but they may have been developed in the first place 

 in connection with adaptation to such factors as food supply. As 

 remarked under O. jennyi, the development of multiple apertures 

 probably led at a later stage to formation of subsidiary chamberlets, 

 such as are found in Heterostegina and Spiroclypeus. 



Ootypes.—V.S.'^M. nos. 497835 and 497836. 



Occurrence. — Guayabal (Tempoal) formation, Claiborne Eocene. 

 Cotypes have been selected from Poza Rica Well no. 8, a further 

 excellent suite of specimens being obtained from core samples of 

 Mecatepec Well no. 6. 



OPERCULINOIDES TUXPANENSIS (Thalmann) 



Plate 16, Figure 2 ; Plate 17, Figuee 2 



1935. Operculina tuxpanensis Thalmann, Eclogae geol. Helvetiae, vol. 28, 



pp. 603-604, figs, a, b (Tuxpam formation, Mexico). 



1936. Operculmoides tuxpanicus Vaughan and Cole, Proc. U. S. Nat. Mus., vol. 



83, p. 494, pi. 37, figs. 4-9. 



