6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.72 



Holotype of vcmety. — {CRt No. 369618), U.S.N.M., from type lo- 

 cality of the Alazan clay, on Rio Buena Vista, Vera Cruz, Mexico, 

 collected by Dr. T. Wayland Vaughan. 



SIPHONINA ADVENA Cushman, var. EOCENICA Cushman and Applin 



Plate 4, fig. 3 



Siphonina advena Cushman, var. eocenica Cushman and Applin, Bull. Ainer. 

 Assoc. Petr. Geol., vol. 10, 1926, p. 180, pi. 9, figs. 16-19. 



This variety differs from the typical form in the less prominent 

 spiral suture on the dorsal side and the more nearly entire periphery ; 

 the chambers not showing as definitely as in the typical. 



Diameter 0.40 mm. ; thickness 0.22 mm. 



The types of this variety are from the Jackson Eocene of Tar Kiln 

 Creek, ^ mile above Neches River, Trinity County, Tex. 



This variety is well distributed in the Upper Eocene of the Gulf 

 Coastal Plain of the United States and occurs in the Alazan of 

 Mexico in material collected by Dr. T, Wayland Vaughan on Rio 

 Tuxpan, 200 meters above the mouth of the Rio Pantepec, Vera 

 Cruz, Mexico. 



SIPHONINA TENUICARINATA Cushman 



Plate 4, fig. 1 



Siphonina tenuicarinata Cushman, Journ. Pal., vol. 1, 1927, p. 166, pi. 26, figs. 

 11, 12. 



Test nearly equally biconvex, periphery very acute and with a 

 broad thin carina, the edge entire except where broken accidentally ; 

 chambers usually five in the last-formed volution, only slightly in- 

 flated on the ventral side ; sutures on the dorsal side not very distinct, 

 especially those of the earlier volutions, on the ventral side nearly 

 radial, slightly depressed ; wall smooth but distinctly perforate ; aper- 

 ture elongate elliptical with a wide lip and short neck. 



Diameter 0.60 mm. ; thickness 0.30 mm. or more. 



Holotype.— {Cat No. 369309 U.S.N.M.) from the typical Alazan on 

 the Rio Buena Vista just south of crossing of Alazan to Moyutla 

 road, collected by Dr. T. Wayland Vaughan, who also collected it at 

 several other stations in the Alazan of Mexico. The figured speci- 

 men which has the keel less developed is from the Ditrupa-hed of 

 Trinidad where the species is also well developed. 



In some of the Mexican material the carina becomes very wide 

 and is more or less wrinkled, giving it the appearance of being 

 costate. 



