GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 81 



peripheral margin broadly rounded, sutures much depressed; wall 

 smooth; aperture circular. 



Length 0.85 mm. 



This species was obtained from the Gatun formation, U.S.G.S. 

 6036, in dark colored, fine grained, sandy clay marl, from Monkey 

 Hill, Mount Hope Station. 



It is unusual in the breaking away of the last formed chamber 

 from the original close coiled method of growth. 



Type-specimen.— -Cat. No. 324720, U.S.N.M. 



Genus SIGMOILINA Schlumberger, 1887. 



SIGMOILINA TENUIS (Czjzek). 



Plate 31, figs. 4a-c. 



Quinqueloculina tenuis Czjzek, Haidinger's Nat. Abhandl., vol. 2, 1847, p. 



149, pi. 13, figs. 31-34. 

 Spiroloculina tenuis H. P>. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 



1884, p. 152, pi. 10, figs. 7-11. 

 Sigmoilina tenuis Sidebottom, Mem. and Proc. Manchester Lit. and Philos. 



Soc, vol. 48, No. 5, 1904, p. 6. 



Description. — Test about twice as long as wide, narrow, compressed, 

 visible chambers 5 or 6 on either side, chambers, narrow, rounded, 

 sutures depressed, distinct; wall smooth, aperture exserted, rounded. 



Length 0.65 nim. Cat. Nos. 324721-3, U.S.N.M. 



Specimens of this species were obtained in the Gatun formation 

 at the following three stations: U.S.G.S. 6033c, in marl from second 

 bed from bottom, just below lower clay, Gatun section, relocated line 

 of the Panama Eailroad; 6035, in gray green, fine grained, sandy 

 shell marl, vicinity of Mindi Hill; and 6036, in dark colored, fine 

 grained, sandy clay marl, from Monkey Hill, Mount Hope Station. 



These three stations have several species in common as will be 

 seen by a glance at the accompanying chart of distribution. 



SIGMOILINA ASPERULA (Karrer). 



Plate 31, figs. 3 a, &. 



Spirolucina asperula Kaeeeb, Sitz. Akad. Wiss. Wien, vol. 57, 1868, p. 136, 

 pi. 1, fig. 10.— H. B. Beady, Rep. Vol. Challenger, Zoology, vol. 9, 1884, 

 p. 152, pi. 8, figs. 13, 14, and 11. 



Description. — Test but slightly longer than wide, very much com- 

 pressed, sutures somewhat indistinct, several chambers visible from 

 each of the flattened sides; wall covered with fine arenaceous parti- 

 cles; aperture exserted, nearly circular. 



Length, 0.8 mm. Cat. Nos. 324724-5, U.S.N.M. 



