492 PROCEEDINGS OF THE NATIONAL, MUSEUM vol. 83 



good specimens may result in the separation of those specimens with 

 14 or 15 chambers from those with 18 or 19. At locality M 55 V, 

 specimens with more chambers, 24 (pi. 38, fig. 3), and more robust 

 tests (pi. 38, fig. 4) were collected. The similarity of these specimens 

 to O. semmesi is obvious. They may represent a variant or they may 

 belong to a closely related but different species. There may be 

 several species of these small specimens of Operculinoides in the 

 Meson formation. 



OPERCULINOIDES ANTIGUENSIS. new species 

 Plate 38, Figures 7-10 



Test of medium size, completely involute, lenticular, symmetrical 

 or asymmetrical with reference to the median plane, edges acute. 

 Diameter, 2.5-3.7 mm; thickness of a specimen 2.5 mm in diameter, 

 1 mm ; of a specimen 3.25 mm in diameter, about 1 mm. 



Sutures are of clear shell material, smooth and usually flush with 

 the surface, radiating as gently curved lines from the center of the 

 test to the periphery. Some of the sutures do not extend to the 

 center but ma}^ converge in groups of three or four, with only one 

 of the group extending to the center. In most specimens there is 

 a small irregular area of clear shell material at the center of the 

 test, and in a few specimens there is a slight boss of clear shell 

 material. 



The variation in the number of chambers in the final volution is 



from 29 in a specimen 3 mm in diameter to 33 in one about 3.5 mm 



*in diameter. The chamber walls in median sections are somewhat 



sigmoid, the proximal end tending to curve forward slightlj'-, the 



outer half strongly recurved. 



Cotypes.—V.S.'^M. no. 495192. 



Localities. — Cotypes, east side of Folly Hill, Nonsuch Bay, An- 

 tigua, collected by W. R. Forrest. The species is also found at 

 numerous other localities in Antigua, one being in the lowest tilted 

 beds, on the beach, at Lynch Point. What appears to be the same 

 species was collected by T. Wayland Yaughan in the Meson forma- 

 tion at locality M 18 V, Hacienda Santa Fe, Topila, near Tampico, 

 Mexico. A specimen in a rock section from this locality is 2.33 mm 

 in diameter and has betv/een 26 and 28 chambers in the last coil. 



Geologic horizon. — Oligocene Antigua formation in Antigua, Brit- 

 ish West Indies; and apparently also in the Oligocene Meson forma- 

 tion of the Tampico Embayment, Mexico. 



Remarks. — For some time the specimens to which the name 

 percuUnoides antiguensis is here applied were placed in 0. sem- 

 onesi^ but further stud}^ of the material has led to the conclusion 



