ART. 20 THE GENUS SIPHOlSTIlsrA AND OTHER GENERA CUSHMAN 3 



the London clay of Southern England as well as at numerous local- 

 ities in the Midway of Texas. 



Siphonma priina Plummer represents the simple type of the genus 

 from which the later more highly developed species have come. 



SPECIES FROM THE EOCENE 

 SIPHONINA WILCOXENSIS, new species 



Plate 2, figs. 1-3 



Test small, nearly circular, biconvex but slightly more inflated on 

 the ventral side, compressed, periphery angled, sharply acute and 

 delicately serrate, slightly lobulate ; chambers usually six in the last- 

 formed volution, slightly inflated on the ventral side; sutures some- 

 what indistinct on the dorsal side, strongly oblique, slightly curved, 

 somewhat marked by the serrate edges of the chambers, not de- 

 pressed, on the ventral side very nearly radial, distinctly depressed; 

 wall smooth, distinctly and coarsely perforate; aperture a small, 

 elliptical opening on the ventral side close to the periphery, with a 

 distinct lip but with the neck only slightly developed or wanting. 



Diameter ujd to 0.30 mm. ; thickness 0.16 mm. 



H olotype.— {C^t. No. 369616 U.S.N.M.), from the Wilcox Eocene, 

 Nanafalia formation, upper portion of Nanafalia Bluff, Tombigbee 

 River, Ala. Similar specimens also occur in the Tuscahoma forma- 

 tion, Bells Landing, Alabama River, Ala., and Tuscahoma Landing, 

 base of bluff, Tombigbee River, Ala. Less well marked specimens 

 occur in the Hatchetigbee formation, McKay's marl bed, Souwashee 

 Creek, 2 miles south of Meridian, Lauderdale County, Miss. 



This species seems to be a derivative from the older Siphonina 

 prima Plummer from which it differs in the somewhat larger size, 

 more convex ventral side, more numerous and narrower chambers, 

 and more strongly developed apertural characters. 



SIPHONINA LAMARCKANA, new species 



Plate 3, fig. 3 



Test small, nearly circular, biconvex but more inflated on the 

 ventral side, somewhat compressed, periphery angled, sharply acute 

 and delicately serrate, slightly lobulate; chambers four in the last- 

 formed volution, inflated on the ventral side; sutures very distinct, 

 strongly oblique and curved on the dorsal side, slightly marked by 

 the serrate edges of preceding chambers, not depressed, on the 

 ventral side nearly radial, depressed; wall smooth with a few 

 distinct scattered larger perforations in addition to the usual fine 

 ones, aperture a comparatively large, broadly elliptical opening on 



