SPECIES OF CAMERINIDAE — BARKER 313 



of the test, the regular nature of the coiling, and the even develop- 

 ment of the walls are well brought out (see pi. 22, fig. 1). 



The species seems to be identical with an undescribed species ob- 

 served in samples from the By ram marl of Byram, Miss, (for which 

 the writer is indebted to Mrs. F. B. Plummer). The nearest de- 

 scribed species seems to be O. vickshurgensis Vaughan and Cole, but 

 O. muiri is considerably thicker than that species (0.7 to 0.9 mm 

 as compared with 0.3 to 0.6 mm) and rather more closely coiled. 

 Dr. T. Wayland Vaughan has examined the types and is of the 

 opinion that the species is new. It has been named after the late 

 John M. Muir, who contributed much toward the elucidation of the 

 stratigraphy of the Tampico region, and whose recent death was 

 felt very deeply by all connected with Mexican stratigraphy and 

 petroleum geology. 



Coty'pes.—V.^:^M. nos. 497839 and 497840. 



OcGun^ence. — ^Lower Alazan (probably restricted to the lower part 

 of Muir's Huasteca formation). 



OPERCULINOIDES ANTIGUENSIS Vaughan and Cole 



Plate 14, Figubes 1, 2; Plate 16, Figure 3; Plate 17, Figuee 1; Plate 21, 



Figures 10, 11 



1936. Operculinoides antiguensis Vaughan and Cole, Proc. U. S. Nat. Mus., 



vol. 83, p. 492, pi. 38, figs. 7-10. 



1937. Camerina sp. B Thiadens, Journ. Pal., vol. 11, p. 95, figs. 3B, 3D, pi. 15, 



fig. 3 (Oligocene, Cuba). 



Test small to medium in size, completely involute, lenticular in 

 cross section, with a rather acute periphery. Diameter (megalo- 

 spheric form), average 2.4 mm, with a maximum observed of 2.8 mm; 

 thickness, average 1.00 mm. The microspheric form (which is fairly 

 plentiful in the Meson outcrops below the Tampico Country Club) 

 is a little larger, averaging 3.5 mm in diameter. 



The sutures, seen from the exterior, are radiating, lying flush 

 with the surface of the test, showing as lines of clear shell material 

 proceeding from a clear central mass. In general, sections show 

 4 whorls, regularly coiled, with a thick outer wall, the final whorl 

 showing 23 to 26 chambers. Exceptional specimens may show 28 

 or 29 chambers in the last whorl. 



The most marked characteristic of the species seen in median, 

 sections is the shape of the septa, w^hich are straight and radial 

 for a little more than half their length and then recurved at an 

 abrupt angle toward the periphery (see figure). This character is 

 well shown by Thiadens's Camerina sp. B (1937, pi. 15, fig. 3), and 

 there seems little doubt that this should be referred to O. antiguensis. 



Plesiotypes.—U.S.^M. nos. 497841 and 497842. 



110179—39 — —2 



