Cytheropteron (Eocijtheropteron) trinitiensis 

 (Vanderpool). Vanderpool, 1933, Jour. Pale- 

 ont., v. 7, p. 410, pi. 49, figs. 16-19. 

 Swain, 1952, U. S. Geol. Survey Prof. Paper 

 234-B, p. 8C, pi. 9, figs. 9, 10. 

 Eocytheropteron trinitiensis (Vanderpool). Cala- 

 han, 1939, Shreveport Geol. Soc. Guidebook 14th 

 Annual Field Trip. 

 Eocytheropteron trinitiensis (Vanderpool). Howe 

 and Laurencich, 1958, Introd. Study Cretace- 

 ous Ostracoda, p. 327, text fig. 

 Shell subovate in side view, highest medially; 

 dorsal margin strongly convex, having a slight 

 angulation on posterior slope at posterior end of 

 hinge line ; ventral margin moderately convex, 

 curving abruptly into anterior but merging grad- 

 ually with posterior margin; anterior margin 

 rather narrowly rounded, extended below ; pos- 

 terior margin acuminately extended as a blunt 

 obliquely upturned caudal process, distinctly con- 

 cave above. Left valve a little larger than right, 

 slightly over-reaching right dorsally and ante- 

 riorly; valves strongly convex, the greatest tu- 

 midity occurs midventrally. Ventral surface of 

 each valve slightly overhangs margin ; along crest 

 of overhanging portion a low ridge occurs. Sur- 

 face ornamented by irregular, branching, low, 

 narrow, widely spaced ridges that are longitud- 

 inally arranged and strongest in ventral half of 

 shell, and are arranged roughly parallel to ter- 

 minal and dorsal margins in dorsal half of shell. 

 Hinge of left valve consists of terminal elon- 

 gate denticulate taxodont sockets and a short, in- 

 tervening weakly crenulate groove ; hinge of right 

 valve correspondingly is formed of terminal elon- 

 gate, slightly elevated taxodont areas and inter- 

 vening edge of valve is weakly crenulate to match 

 short groove in left. Inner lamellae of moderate 

 width, line of concrescence and inner margin co- 

 incide except ventroterminally, where they are 

 slightly separated. Radial canals few and widely 

 spaced. Muscle scar consists of an anteromedian 

 vertical row of four small spots and two addition- 

 al spots lying anterior to ends of main group. 



Length of holotype shell (PI. 5, Fig. 4d) 0.74 

 mm, height 0.48 mm, convexity 0.46 mm. 



Remarks. — The specimens from the Paluxy For- 

 mation, three miles north of Marietta, Oklahoma 

 have not been seen by the writers and, as suggest- 

 ed by Howe and Laurencich (1958, p. 327), may 

 not be conspecific with trinitiensis because of dif- 

 ferent surface ornamentation. 



Occurrence. — The species was described from 

 the Glen Rose Formation, eight miles west of 

 Weatherford, Texas (Vanderpool, 1928, p. 106), 

 and also occurs in the Glen Rose and DeQueen 

 Formations of Arkansas and northwestern Louisi- 

 ana and the Trinity (?) and pre-Trinity (?) of 

 the North Carolina subsurface. 



Genus Orthonotacythere Alexander, 1933 



Orthonotacythere delicatula Swain and Brown, 



n. sp. 



Plate 3, Figures 15a-c 



Shell subquadrate-acuminate in side view, high- 

 est about one-fifth from anterior end ; dorsal mar- 

 gin straight, about three-fourths of shell length, 

 with distinct, moderately obtuse anterior, and 

 more broadly obtuse posterior, cardinal angles; 

 ventral margin straight, subparallel to and about 

 the same length as dorsal margin; anterior mar- 

 gin broadly rounded, somewhat extended below, 

 subtruncate above; posterior margin with com- 

 pressed bluntly pointed, caudate process extended 

 above midheight. Left valve larger than right, 

 overlapping and overreaching right terminally 

 and dorsally. Valves moderately inflated, greatest 

 convexity posteromedian. 



Anterior and posterior marginal zones sharply 

 compressed, free margins provided with narrow 

 thickened low rims. General surface with a prom- 

 inent dorsomedian high node, and anterodorsal 

 lower node ventrad of small eye tubercle, a pos- 

 terodorsal node, and a ventral row of four nodes 

 so arranged as to almost form a ridge, the next 

 to posterior node the highest, the two anterior 

 nodes cleatlike. Ventral surface flattened anteri- 

 orly, overhangs margin posteriorly and is orna- 

 mented with several longitudinal low narrow 

 ridges ; median surface of valves densely and fine- 

 ly pitted and with a few weak irregular ridges. 



Internal features not seen in the two complete 

 specimens at hand. 



Length of holotype shell 0.68 mm, height 0.40 

 mm, convexity excluding node 0.23 mm, convexity 

 including node 0.40 mm. 



Relationships. — The general shape and pattern 

 of ornamenting nodes are similar to O. harmed 

 (Israelsky) (1929, p. 12) from the Upper Creta- 

 ceous of Arkansas, but that species lacks the 

 sharply acuminate posterior extension of the pres- 

 ent form. O. sulcata Brown (1957, p. 23) from the 

 Black Creek Formation of North Carolina is sim- 



40 



