Eocytheropteron cf. tumidum Alexander 



Plate 3, Figure 13 



Ci/theropteron tumidum Alexander, 1929, Univ. 



Texas Bull. 2907, p. 103, pi. 10, figs. 16, 17. 

 Cytheropteron (Eocytheropteron) tumidum Alex- 

 ander, 1933, Jour. Paleont., v. 7, p. 199, pi. 27, 



figs. 13a, b. 

 Eocytheropteron tumidum Calahan, 1939, Shreve- 



port Geol. Soc. Guidebook 14th Annual Field 



Trip, p. 49, pi. 7, fig. 7. 



Howe and Laurencich, 1958, Introd. Study 

 Cretaceous Ostracoda, p. 328, text fig. 



Shell almond-shaped in side view, highest an- 

 teromedially ; dorsal margin moderately convex; 

 ventral margin gently convex; anterior margin 

 rounded, slightly extended below ; posterior mar- 

 gin narrower and with compressed, prominently 

 extended, but short, blunt median caudal process. 

 Valves strongly convex, the greatest inflation mid- 

 ventral, where surface overhangs ventral margin. 

 Left valve a little larger than right, overlapping 

 along dorsal and anterior margins. 



Ventral portion of each valve bears a narrower 

 sub-alate ridge; between ridge and ventral mar- 

 gin, valve surface flattened but slightly overhangs 

 ventral margin; ventral surface bears low narrow 

 longitudinal ridges between which interspaces are 

 weakly pitted. 



Internal characteristics not seen in specimens 

 available for study. 



Length of figured specimen 0.58 mm, height 

 0.36 mm, convexity 0.38 mm. 



Remarks. — The general shape and surface orna- 

 mentation of this form are closely similar to 

 Eocytheropteron tumidum Alexander, but the 

 preservation of the Florida specimen is poor and 

 the internal features are unknown. 



Occurrence. — Lower member of Atkinson For- 

 mation, Sun Oil Company's No. 1 Johnson well, 

 Columbia County, Florida, core sample 2,955- 

 2,965 feet. The species was described from the 

 Goodland and Kiamichi Formations of Texas and 

 has been recorded from the Lower Cretaceous of 

 northern Louisiana. 



Eocytheropteron semiconstrictum Alexander? 

 Plate 3, Figures 14a, b 



Cytheropteron (Eocytheropteron) semiconstrict- 

 um Alexander, 1933, Jour. Paleont., v. 7, p. 198, 

 pi. 26, fig. 8. 



Eocytheropteron semiconstrictum (Alexander). 



Howe and Laurencich, 1958, Introd. Study 



Cretaceous Ostracoda, p. 327, text fig. 



Shell ovate-pyriform in lateral view, highest 

 anteromedially ; dorsal margin strongly convex, 

 sloping nearly uniformly in front of and behind 

 position of greatest height; ventral margin mod- 

 erately convex, bending more gradually into pos- 

 terior than into anterior margin ; anterior mar- 

 gin broadly rounded, slightly extended below. 

 Valves relatively compressed; greatest convexity 

 ventromedian in position. Left valve slightly larg- 

 er than and extending beyond edge of right dor- 

 sally. 



Posterior margin more narrowly rounded, with 

 median blunt caudal process, lateral margins of 

 which produce slight concavities in shell margin. 

 Anteromedially, a shallow subvertical sulcus ex- 

 tends from position of greatest height to mid- 

 height. General surface bears a series of weak 

 ridges parallel to anterior and ventral margins 

 and midportion of valves is weakly reticulate. 

 Ventral portion of valve surface formed into 

 longitudinal swellings that slightly overhang ven- 

 tral margin and produce a flattened venter, in 

 which the valve contact is slightly incised medi- 

 ally. 



Internal features of shell not observed. 



Length of figured specimen (PI. 3, Fig. 14a) 

 0.43 mm, height 0.26 mm, convexity 0.25 mm. 



Remarks. — The general shape, convexity, sur- 

 face ornamentation and median sulcus of this 

 species furnish a comparison with E. semicon- 

 strictum Alexander. The dorsal slopes and inte- 

 rior curvature of the posterior margin are slight- 

 ly different from that described by Alexander, 

 features which may be ascribed to individual vari- 

 ation. The lack of information about internal 

 characteristics prevents more definite identifica- 

 tion of the present specimens. 



Occurrence. — Lower member of Atkinson For- 

 mation, Magnolia Petroleum Company's No. 5B, 

 State Block 1A, Franklin County, Florida, core 

 sample 5,138-5,144 feet. The species was described 

 from the Kiamichi Formation of northeastern 

 Texas. 



Eocytheropteron trinitiensis (Vanderpool) 



Plate 5, Figures 4a-e, 5a-c; Text Figure lid 



Cytheridea trinitiensis Vanderpool, 1928, Jour. 

 Paleont., v. 2, p. 106, pi. 14, figs. 3-6. 



39 



