ART. 3 NEW SPECIES OF FOKAMINIFERA VAUGHAN 15 



preserved. It appears that the more usual condition is for walls of 

 chambers in adjacent annuli to be in alignment, but that this con- 

 dition is not invariable. The length of the chambers usually exceeds 

 the width. The equatorial la3^er is very thin, only about 15^t tall 

 near the center and about twice as tall near the periphery. 



The lateral chambers are very low, the cavities being small. There 

 are seven or eight, possibly nine, layers over the center, the number 

 decreasing to about two at the periphery. The thickness of the walls 

 separating the layers exceeds the height of the chambers, which is 

 about 7m, while the walls range from about 14 fx to 21)u thick. The 

 length of the chambers is variable, but it is several times the height. 

 The chamber ends are not clearly marked, but are formed by succes- 

 sive overlapping of walls. There are no clearly developed pillars, but 

 there are on the outer surfaces of the chamber walls small papilliform 

 elevations. 



Localities and geologic horizon. — Arroyo Guadalupe, 50 miles north- 

 west of La Paz, Lower California, collected by J. H. Clopton, for 

 whom the species is named. Tepetate formation, middle or upper 

 Eocene. 



Dr. W. S. W. Kew, in connection with investigations he conducted 

 for the Marland Oil Co., collected specimens in the Eocene Tepetate 

 formation and presented them to the United States National Museum. 

 The following is a list of the U. S. G. S. locality numbers and the 

 localities: 9687, Arroyo Lievre, about 5 km. east of Rancho Saucito; 

 9696, Arroyo Colorado; 9697, 1 mile northeast of Rancho Colorado, 

 in Arroyo Colorado (upper part of Tepetate formation) ; 9698, Arroyo 

 Colorado, at ranchito northwest of Cerro Colorado (near top of 

 Tepetate formation) ; 9706, Arroyo Colorado, above Rancho Colorado 

 (upper beds of Tepetate formation). 



This species seems to be the one previously referred to "Orthoprag- 

 mina" pratti (Michelin) by Prof. H. Douville, basing his determination 

 on specimens collected by Dr. A. Heim^ in Lower CaHfornia along 

 Arroyo Colorado in the Tepetate formation. A large suite of 

 Discocyclina pratti is in the collections of the Scripps Institution, and 

 D. cloptoni is decidedly different. D. cloptoni is not umbonate and 

 its embryonic apparatus is peculiar, as well as differing in other 

 respects. 



Types.— Coij^e^ (Cat. No. 371011, U.S.N.M.), the figured speci- 

 mens collected by Mr. Clopton on Arroyo Guadalupe. Topotypes, 

 in the Scripps Institution of Oceanography. 



•Douvill6H., Les orbitoides de la presqu'Ile de Californie, Acad. Sci. Compt. Rend., vol. 161, p. 109, 

 1915; Heim, A., Sur la geologie de la partie meridionale de la basse Californie, Compt. Rend., vol. 161» 

 p. 119; Heim, A., Notes ou the Tertiary of Southern Lower California, Geol. Mag., vol. 59, p. 529, 1922 

 (see especially pp. 534-5). 



