lateral punctate ridge. In both male and female 

 dimorphs the ridge may be sharply truncate pos- 

 teriorly or may merge gently into the posterior 

 third of the valve. Striations on the ventral sur- 

 face vary from strong to weak, generally being 

 more pronounced on the shorter tumid females. 

 Schmidt (1948, p. 414) has recently described 

 the species. 



Br achy cy there nausiformis Swain 

 Plate 4, Figures 3, 4 



Br achy cy there nausiformis Swain, 1952, U. S. 

 Geol. Survey Prof. Paper 234-B, p. 80, pi. 8, 

 figs. 44-47. 



The external features of this species were ade- 

 quately described by Swain (1952, p. 80). 



Hinge of right valve consists of a high pointed 

 tooth and postjacent socket; attached is a finely 

 crenulate bar, thicker anterad, extending to a 

 weakly notched, elongate posterior tooth project- 

 ing high on the dorsal margin. Hinge of left valve 

 consists of an anterior socket and postjacent high 

 pointed tooth ; attached is a finely crenulate bar. 

 thicker anterad, extending to a weakly crenulate 

 socket. Anterior tooth and crenulate bar are sep- 

 arated from the dorsal margin by a depressed 

 furrow, widest anterad and merging into crenu- 

 late socket posterad. Line of concrescence and 

 inner margin coincide. Anterior marginal pore 

 canals, about 34 in number, finely bifurcated. Pos- 

 terior marginal pore canals, 12 in number, 

 straight and slightly coarser than anterior ca- 

 nals. Deep muscle pit located anterior median- 

 third of valve. 



Dimensions: Fig. 3: length 1.02 mm; height 

 0.52 mm; convexity 0.24 mm. 



Occurrence: Black Creek only. Swain lists the 

 occurrence in beds of Black Creek ( ?) and Eutaw 

 (?) age. Localities G, H, I, J, and K. U.S.N.M. 

 128929, 128930. 



Brachycythere plena Alexander, 1934 

 Plate 4, Figure 7 



Brachycythere plena Alexander, 1934, Jour. 

 Paleontology, vol. 8, p. 216-217, pi. 33, fig. 6. 

 Murray and Hussey, 1942, Jour. Paleontology, 



vol. 16, p. 176, pi. 27, figs. 2, 5, 6, text fig. 



2, figs. 3, 7. 

 Kline, 1943, Mississippi Geol. Survey, Bull. 



53, p. 67-68, pi. 8, fig. 3. 

 Van den Bold, 1946, Cont. Study Ostracoda, 



p. 108, pi. 13, figs. 4-5. 

 Harris and Jobe, 1951, Microfauna Midway 



Ark., p. 71, pi. 12, fig. 6. 

 Munsey, 1953, Jour. Paleontology, vol. 27, 

 p. 11, pi. 3, figs. 17-21. 

 Dimensions: Fig. 7: length 1.06 mm; height 

 0.53 mm; convexity 0.30 mm. 



Occurrence : Peedee only at surface. Peedee and 

 unnamed Paleocene units in the subsurface. Lo- 

 calities A and E. U.S.N.M. 128931. 



Remarks : The species has been adequately de- 

 scribed by Alexander (1934, p. 216-217). The 

 present specimens show the strength of the ven- 

 trolateral ridge and "crescent-shaped" sulcus to 

 be variable within narrow limits. In addition, our 

 specimens show a tendency toward a faintly 

 wrinkled or reticulate midportion adjacent to the 

 ventro-lateral ridge. 



Brachycythere ledaforma (Israelsky) 

 Plate 4, Figure 6 



Cytheropteron ledaforma Israelsky, 1929, Ar- 

 kansas Geol. Survey Bull. 2, p. 8, pi. 1A, figs. 

 5-7. 

 Cythere acutocaudata Alexander, 1929, Texas 



Univ. Bull. 2907, p. 87, pi. 7, figs. 5, 6. 

 Br achy cy thence ledaforma (Israelsky) Alexan- 

 der, 1933, Jour. Paleontology, vol. 7, p. 206, 

 pi. 25, fig. 9 ; pi. 27, fig. 20. 

 Brachycythere ledaforma (Israelsky) Jennings, 

 1936, Bull. Am. Paleontology, vol. 23, no. 78, 

 p. 49, pi. 6, fig. 15. 

 Shell in side view, subtriangular ; widest at an- 

 terior cardinal angle ; dorsal margin strongly 

 arched, straight along hinge; ventral margin 

 straight, slightly incised at antero-ventral junc- 

 tion ; anterior margin broadly and obliquely 

 rounded; posterior margin, compressed, triangu- 

 lar, with acute postero-ventral angle. Midportion 

 strongly inflated, alate, and sharply truncate 

 along venter ; right valve with a short ridge sur- 

 mounting ala; left valve more tumid, without 

 ridge ; a well defined furrow separates the anterior 

 fourth from the tumid midportion, terminating 

 dorsally, posterad of a subdued eye tubercle at 

 the anterior cardinal angle. Surface variable, 

 smooth to finely reticulate or punctate medially; 

 venter with about six fine ridges or striations ; a 

 short spine present at acute posterior angle. In- 

 ternal features those of the genus. 



Dimensions: Fig. 6: length 0.64 mm; height 

 0.26 mm. 



12 



