136 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1921. 



Specimens were obtained at five of the six 

 Mint Spring marl stations, as follows: 



6448. Glass Bayou, Vicksburg, Miss. 

 6451, 6452. Mint Spring Bayou, Vicksl)urg, Miss. 

 6647. Chickasawhay River 1} miles southwest of Boice, 

 Miss. 

 7671. "Brown's Cave," Leaf River, Miss. 



This species is common both in the Tertiary 

 and in the present oceans. I have recorded 

 it from the Pliocene and the Miocene of the 

 Coastal Plain of the United States and the 

 Oligocene (Byram marl) at Byram, Miss. 



Truncatulina byramensis Cushman. 



TruncatuUna byramensis Cushman. U. S. (t^ol. Survey 

 Prof. Paper 120, p. 96, pi. 20. figs. 4-6, 1022. 



Test plano-convex, dorsal side slightly con- 

 vex, ventral side flattened, peripheral margin 

 subcarinat* ; about eight chambers in the last- 

 formed whorl, chambers on the ventral side 

 failing to reach the center of the test, leaving 

 a definite umbilical area, which is filled with 

 clear shell material; on the dorsal side each 

 chamber at its inner border has the angles 

 somewhat produced and a broad, rounded 

 reentrant near the middle; on the ventral side 

 the inner half of the chamber is rather intri- 

 cately lobed, the chambers themselves of 

 lighter color; the sutures darker, of clear shell 

 material; surface finely granular; aperture an 

 elongate opening at the base of the last-formed 

 chamber near its inner ventral border. Diam- 

 eter 0.35 to 0.75 milluneter. 



Specmiens of this species were collected at 

 the following stations: 



6451, 6452. Mint Spring Bayou, Vicksburg, Miss. 

 6447, 6448. Glass Bayou, Vicksburg, Miss. 



This species was described from specimens 

 obtained in the Byram marl, where it is com- 

 mon. It is a peculiar species, easily distin- 

 guished by the unusual lobed chambers. 



Truncatulina americana Cushman var. 



Truncatulina anuricana Cushman, U. S. Geol. Survey 

 Bull. 676, p. 63, pi. 20, figs. 2, 3; pi. 21, fig. 1. 1918; 

 U. S. Nat. Mus. Bull. 103, p. 68, pi. 23, figs. 2 a-c, 

 1918; U. S. Geol. Survey Prof. Paper 120, p. 97, 

 pi. 20, figs. 7, 8. 1922. 



Test plano-convex, dorsal side nearly flat, 

 ventral side slightly convex; chambers numer- 

 ous, ten to fifteen in the last-formed coil, rather 

 rapidly increasing in size, peripheral margin 

 subangular, dorsal side with the last few cham- 

 bers failing to meet the umbilicus, ventral side 



similar in this respect in most specimens; su- 

 tures distinct, slightly limbate on the dorsal 

 side, tlepressed on the ventral side; wall smooth, 

 punctate, aperture peripheral with a slight lip. 

 Diameter 0.75 millimeter or less. 



Small specimens of this species with a slightly 

 broader form than the typical occur in the 

 Mint Spring marl at the following stations: 



6447, 6448. Glass Bayou, Vicksburg, Miss. 



6451, 114.52. Mint Spring Bayou, Vicksburg, Miss. 



This species is found in the Miocene and 

 Oligocene of the Coastal Plain and in the upper 

 Oligocene of the Canal Zone. 



Truncatulina pseudoungeriana Cushman. 



Triinciilulijia ungeriana U. B. Brady (not Rotalina unger- 

 iann D'Orbigny, 1826), Chalknger Kept., Zoology, 

 vol. 9, pi. 94, figs. 9 a-c, 18S4. 

 Cushman, U. S. Nat. Mus. Bull. 103, p. 69, pi. 24, fig. 

 1, 1918. 



Trunnitulina pseudoungeriana Cushman. U. S. Geol. Sur- 

 vey Prof. Paper 129, p. 97, pi. 20. fig. 9, 1022. 



Test biconvex, almost ecjually so, periphery 

 subacute; chambers nine to eleven in the last- 

 formed whorl, those of the earlier whorls not 

 showing on either the ventral or the dorsal 

 side, on the dorsal because they are hidden by 

 the roughness of the surface, and on the ventral 

 because of the involute character; periphery 

 lobulate; sutures distinct above in the last 

 whorl and very distinct below, as the sutures 

 are somewhat tumid on the ventral side; um- 

 bilical region filled nearly flush with the cham- 

 bers by clear shell material, last few chambers 

 on the dorsal side slightly above the surface on 

 the inner margin; surface dorsally with coarse 

 punctae, below smooth and more finely punc- 

 tate; aperture at the periphery. Diameter 

 1 millimeter or less. 



Specimens of this species were common in 

 the Mint Spring marl at station 6647, Chicka- 

 sawhay River 1 5 miles southwest of Boice, 

 Miss. It occurred more rarely at the following 

 stations: 



C447. Glass Bayou, Vicksburg, Miss. 



6451. Mint Spring Bayou, Vicksburg, Miss. 



7671. "Brown's Cave," Leaf River, Miss. 



Truncatulina vicksburgensis Cushman, n. sp. 



Plate XXXV, figures 7, 8. 



Test plano-convex, dorsal side with the 

 sutures very obscure, low-spired, periphery 

 subacute, ventral side with a central raised 

 area and the inner angle of each chamber end- 

 ing in a raised knob, ventral side of the chara- 



