ART. 20 THE GENUS SIPHONINA AiSTD OTHER GENERA CUSHMAN 7 



SPECIES FROM THE OLIGOCENB 

 SIPHONINA ADVENA Cushman 



Plate 1, figs. 7 Or-c 



Siphonina advena Cushman, U. S. Geol. Survey Prof. Paper 129, 1922, pp. 98, 

 137, pi. 22, figs. 1, 2 ; Prof. Paper 133, 1923, p. 42. 



Test biconvex, the ventral side more convex than the dorsal, pe- 

 riphery subacute, with the keel not usually strongly developed; 

 chambers usually five in the last- formed volution; sutures on the 

 dorsal side flush with the surface, somewhat limbate, ventrally 

 nearly radial, but slightly curved, very slightl}'^ depressed; wall 

 smooth, very distinctly perforate, the perforations often in lines 

 giving a distinctive appearance to the test; aperture elliptical, with 

 a distinct neck and broad lip. 



Diameter 0.50 mm. ; thickness 0.20 mm. 



This is an abundant species in all the members of the Lower 

 Oligocene, Vicksburg, of the Gulf Coastal Plain of the United States 

 occurring in the Byram calareous marl, Glendon limestone, Mari- 

 anna limestone, Mint Spring marl, and Red Bluff clay in Mississippi, 

 Alabama, and Florida. The figured specimen is an especially well- 

 preserved one from the Byram marl. 



Specimens apparently of this species were collected by Dr. T. 

 Wayland Vaughan from the Oligocene of Mexico along the Trans- 

 continental Railroad east of Los Naranjos. 



SPECIES FROM THE MIOCENE 

 SIPHONINA RETICULATA (Czjzek) 



Plate 1, figs. 1 a-e, 2 o-c; plate 3, figs. 4 a-c 



Rotalina reticulata Czjzek, Haidinger's Nat. Abh., vol. 2, 1848, p. 145, pi. 13, 



figs. 7-8. 

 Siphonina reticulata Brown, Lethaea Geognostica, ed. 3, vol. 3, 1853-1856, 



p. 227, pi. 35, figs. 23 a-o. 

 SipTionina fimhriata Reiuss, Denksehr. Akad. Wiss. AVien, 1849, p. 372, pi. 47, 



fig. 6. 



Test nearly equally biconvex, somewhat compressed, periphery 

 angled; usually four chambers in the last-formed volution, only 

 slightly inflated ; sutures depressed slightly on the ventral side, radial, 

 on the dorsal side curved, strongly marked by the fimbriation of the 

 periphery of the chambers; aperture elliptical, with a distinct lip 

 and well marked, contracted neck. 



Diameter 0.50 mm. ; thickness 0.25-0.30 mm. 



The type species of the genus is /Siphonina -fimhriata Reuss but 

 this is obviously a synonym of the earlier described S. reticulata 



