320 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 86 



The following description, though to some extent a repetition of 

 that of Vaiighan and Cole, is based on a larger collection of ma- 

 terial, including specimens from near Tempoal, Veracruz, and from 

 near Tantoyuca, Veracruz. 



Test small, flattened, very thin, involute, septa raised, somewhat 

 limbate, and broken up into large tubercles. The poles of the test 

 also show a group of tubercles, or a large central tubercle surrounded 

 by small beads. A well-developed keel gives the test a rather trun- 

 cated periphery. Diameter, up to 2.0 mm, average 1.8 mm. 



Sections show regular, rather open coiling, with 2i/^ to 3 whorls, 

 with 15 to 20 chambers in the final whorl. The septa are thin and 

 nearly straight for one-half to two-thirds of their length, then 

 gently curved toward the periphery. Chambers not very numerous, 

 with a rather rectangular appearance. 



This species was long considered to be a variety of 0. mariannensis 

 Vaughan (1928), from which it differs principally in the possession 

 of a greater number of chambers, a thicker test and generally more 

 robust form, but it is considered by Vaughan and Cole to rank as 

 a distinct species. In spite of the thinness of the test and the clear 

 marking of all whorls on the exterior, I believe that this species 

 should be referred to Opercidirwkles. This is supported by 

 Hanzawa's placing the closely allied O. mariannensis in that genus and 

 by the involute nature of the test shown by the transverse sections 

 figured by Vaughan and Cole (193G, pi. 35, figs. 3, 3a, and 4). My 

 preparations also show this involute character. 



PJesiotypes.—V.^.'^M. nos. 407866, 409868, and 497869. 



Other specimens. — U.S.N.M. no. 497867. 



OcGwrreThce. — Tantoyuca formation, Jackson Eocene. 



OPERCULINOIDES CATENULA (Cushman and Jarvis) 



Plate 14, Figures 6, 8; Plate 18, Figuke 5; Plate 21, Figures 7, 8 



1932. OpercuUna catcnula Cushman and Jakvis, Proc. U. S. Nat. Mas., vol. 80, 

 art. 14, p. 42, pi. 12, fig.s. 13a-b. 



Description of ^Mexican specimens ascribed to this species is as 

 follows : 



Test small to medium in size, compressed lenticular, completely 

 involute, with a strongly developed rounded keel. The sutures (on 

 rather weathered specimens) show as raised radiating ribs, irregu- 

 larly beaded, with a strong umbonal boss. Diameter, up to 3.0 mm 

 (average 2.5 mm for 5 specimens) ; thickness, 0.7 to 0.85 mm (cf. 

 diameter 2.25 mm, thickness 0.6 mm for O. catenula). 



Sections show a rather loosely coiled test of 2 to 2i/4 whorls with 

 17 to 22 chambers in the final whorl (compare 15 chambers in the 



