Florida, core sample 3,834-3,838 feet; (2) Hum- 

 ble Oil and Refining Company's Tindel No. 1 well, 

 core sample 3,470-3,500 feet; (3) Sun Oil Com- 

 pany's Johnson No. 1 well, Columbia County, 

 Florida, core sample 2,955-2,965 feet; (4) Sun 

 Oil Company's No. 1 Crapps "A" well, Dixie Coun- 

 ty, Florida, core sample 3,548-3,556 feet; (5) 

 Humble Oil and Refining Company's Bennett and 

 Langdale No. 1 well, Echols County, Georgia, core 

 sample 3,690-3,700 and 3,700-3,710 feet. 



Cythereis praeornata Swain and Brown, n, name 



Plate 5, Figures 6a-c; Text Figure 10b 



Cythere ornata Vanderpool, 1928, Jour. Paleont., 



v. 2, p. 106, pi. 14, figs. 7, 8. 

 not Cythere ornata (Bosquet). Bosquet, 1954, 



Crust. Foss. du Terr. Cret. du Duche de Lim- 



bourg, Comm. desc. et geol. carte. Neerlande, 



Mem., v. 2, p. 102, pi. 9, figs. 8a-d. (fide Howe 



and Laurencich, 1958). 



Shell subquadrate in side view, highest about 

 one-fourth from anterior end ; hinge margin near- 

 ly straight, concave medially due to projection of 

 anterior cardinal area; anterior cardinal angle 

 more obtuse than posterior; ventral margin also 

 nearly straight, slightly concave medially and con- 

 verging slightly with dorsum toward posterior; 

 anterior margin broadly curved, slightly extended 

 below and bears short spines or nodes ; posterior 

 margin narrowly curved, extended medially, with 

 four or five short thick spines below and truncate 

 above. Valves subequal, left apparently a little 

 larger than right, and overlapping right along 

 dorsal terminal slopes, although complete cara- 

 pace not seen. Valves relatively strongly com- 

 pressed, greatest convexity posteromedian. 



Anterior margin and adjacent part of ventral 

 margin bear a high rather narrow submarginal 

 rim; dorsally rim terminates in prominent eye 

 tubercle; ventrally, rim passes with slight offset 

 into ventral low alaform ridge that has another 

 narrow low ridge ventral and parallel to it ; these 

 two terminate about one-fifth from posterior end, 

 and are connected at their posterior ends by a 

 thick, elevated cross ridge; mid-dorsally is a sub- 

 marginal ridge that arises a little in front and 

 ventrad of eye tubercle and terminates posteriorly 

 in a thickened and elevated, ventrally pointing 

 spur; a large, strongly elevated anteromedian tu- 

 bercle slopes gently on its anterior flank and 

 steeply on its posterior side where it is defined by 

 a curving row of five or six pits ; posterior to sub- 



median node is a second smaller node ; general 

 valve surface in holotype ornamented by narrow 

 reticulating ridges. 



Hinge of right valve consists of an anterior, 

 high, knoblike, somewhat elongate tooth, a pos- 

 teriorly adjacent triangular socket, an interter- 

 minal valve-edge rabbeted above, and a posterior 

 elongated high ridgelike tooth ; hinge of left valve 

 has opposite features to those of right valve. In- 

 ner lamellae of moderate width, line of concres- 

 cence and inner margin mainly coincide but are 

 slightly separated terminally. Radial canals nu- 

 merous (about 35) closely spaced and tend to 

 occur in pairs anteriorly, less numerous posterior- 

 ly. Muscle scar not seen. 



Length of holotype left valve (PI. 5, Fig. 6a) 

 1.03 mm, height 0.53 mm, convexity of valve 0.27 

 mm. 



Remarks. — This species is close to the general 

 group of Cythereis ornata (Bosquet) (1847, p. 

 21) in shape and surface ornamentation, in fact 

 one wonders whether Vanderpool might not have 

 intended to refer his specimens from Arkansas 

 to Bosquet's species rather than to assume author- 

 ship of his Cythereis ornata. Bosquet's ornata, 

 however, is according to Veen (1936, p. 3) (fide 

 Howe and Laurencich, 1958, p. 219) more coarse- 

 ly reticulate and has a different pattern of ventral 

 ridges than the present form. 



Occurrence. — The type specimens are from the 

 DeQueen Limestone Gypsum Bluff, near Mur- 

 freesboro, Pike County, Arkansas. According to 

 Vanderpool (1928, p. 107) the species also occurs 

 in the Glen Rose Formation. 



Family Cytheruridae G. W. Midler, 1894 



Genus Eocytheropteron Alexander, 1933 



Eocytheropteron greenvillensis 

 Swain and Brown, n. sp. 



Plate 3, Figures lla-e; Text Figures lib, c 



Shell, short and high, subpyriform in side view, 

 highest posteromedially ; dorsal margin strongly 

 convex, umbonate, anterior slope truncate, pos- 

 terior slope steep and concave; ventral margin 

 varies from nearly straight or somewhat sinuous 

 in right valve to slightly convex in left valve ; an- 

 terior margin narrowly rounded, strongly extend- 

 ed below ; posterior margin broader, with short, 

 upward pointing caudal process a little above 

 midheight. Left valve larger than right, extend- 

 ing strongly beyond edge of right dorsally and 



35 



