126 PROCEEDINGS OF THE NATIONAL MUSEUM vol.77 



right side of ridge, the left set crossing the ridge and bending in a gen- 

 tle curve backward, while those on the right begin at the right of the 

 ridge and extend backward in a more nearly direct fashion, both sets 

 reaching the periphery and giving the shell only a semiequitant ap- 

 pearance, the two sides so nearly equal as to give a bilateral sym- 

 metry; aperture round, radiate, the apertural end showing four 

 chambers. 



Length of holotype, 0.70 mm. ; width, 0.32 mm. ; thickness, 0.12 mm. 



Holohjpe.— Cat. No. 371021, U.S.N.M. 



It differs from any other known Sigmomorphina in its strongly 

 inflated longitudinal ridge developed in the portion corresponding to 

 the line of the apertures of each of the sigmoid series of chambers. 



Distribution. — Eocene, 17K miles south of Palestine Road on 

 Grapeland Road, first creek crossed hj fording north of Grapeland, 

 Houston County, Tex. It occurs in the Mount Selman and Cooks 

 Mountain greensands of the Eocene of Texas. 



SIGMOMORPHINA REGULARIS (v. Munster) 



Plate 33, figures 1 a, h 



Polymorphina regularis v. Munster, in Roemer, Neues Jahrb. fiir Min., etc., 

 1838, p. 385, pi. 3, fig. 21.— Reuss, Sitz. Akad. Wiss. Wien, vol. 18, 1855 

 (1856), p. 247, pi. 7, figs. 70-73.— H. B. Brady, Parker, and Jones, 

 Trans. Linn. See, vol. 27, 1869, p. 229, pi. 40, figs. 13 a-c— Weller, 

 Geol. Surv.New Jersey, Paleontology, vol. 4, 1907, p. 253, pi. 3, figs. 

 29-31. 



Polymorphina anceps Philippi, Beitr. Kennt. Tert. nordwest. Deutschlands, 

 1843, p. 41, pi. 1, fig. 34.— Reuss, Sitz. Akad. Wiss. Wien, vol. 18, 

 1855 (1856), p. 246, pi. 6, fig. 68; pi. 7, fig. 69; vol. 50, abt. 1, 1864, 

 p. 472, pi. 3, figs. 11, 12; pi. 4, figs. 1-3; Denkschr. k. Akad. Wiss. 

 Wien, vol. 25, 1865, p. 155, pi. 4, figs. 9-11.— H. B. Brady, Parker, 

 and Jones, Trans. Linn. Soc, vol. 27, 1870, p. 223, pi. 39, fig. 8 a-c. 



Polymorphina compressa Philippi, Beitr. Kennt. Tert. nordwest. Deutsch- 

 lands, 1843, p. 69, pi. 1, fig. 35. 



Polymorphina humboldti Bornemann, Zeitschr. deutsch. geol. Gesell., vol. 

 7, 1855, p. 347, pi. 18, figs. 7, 8. — H. B. Brady, Parker, and Jones, 

 Trans. Linn. Soc, vol. 27, 1870, p. 236, pi. 40, figs. 21 a, 6.— Reuss, 

 Sitz. Akad. Wiss. Wien, vol. 62, pt. 1, 1870, p. 488.— v. Schlicht, 

 Foram. Septar. Pietzpuhl, 1870, pi. 32, figs. 23-26, 29-32, 35-38. 



Test oval (young) to oblong (adult), compressed, broadest in the 

 upper half, margin angular; chambers compressed, long, arranged in 

 a clockwise, sigmoid series, each succeeding chamber removed much 

 farther from the base; sutures not depressed, limbate; wall smooth, 

 translucent; aperture radiate. 



Maximum length of our specimens, 2.70 mm.; breadth, 1.20 mm.; 

 thickness, 0.65 mm. 



This species has been described by German authors under differ- 

 ent names as the above synonymy shows. This is not surprising; 



