Subdued subcentral node. Anterior third bears 

 two rows of coarse reticulations, one row of which 

 passes along and continues on underside of the 

 dorsal ridge. Middle and anterior thirds punctate. 

 Hingement and musculature that of the genus. 



Dimensions : Fig. 22 : length 0.72 mm ; height 

 0.35 mm; biconvexity 0.16 mm. 



Occurrence: Peedee only, localities A and C. 

 U.S.N.M. 128958, 128959, 128960, 128961. 



Remarks : The flat compressed carapace, hinge- 

 ment, marginal rims, and very subdued subcen- 

 tral node of this species place it in the genus 

 Platycythereis Triebel. The writer has compared 

 the more strongly spinose molts identified by 

 Schmidt as Paracythereis semilenis Schmidt with 

 the species at hand and considers them to be con- 

 specific. 



Genus Protocythere Triebel, 1938 

 ■ Protocythere paratriplicata Swain 

 Plate 3, Figures 16, 17 



? Cythere fo&rsteriana Bosquet, Alexander, 

 1929, Texas Univ. Bull. 2907, p. 82, pi. 6, 

 figs. 1, 11. 



(Not) Bosquet, 1847, Mem. Soc. Roy. Sci. 

 Liege, nol. 4, p. 364, pi. 2, figs. 4a-d. 

 Protocythere paratriplicata Swain, 1952, U. S. 

 Geol. Survey Prof. Paper 234-B, p. 85, pi. 9, 

 figs. 18-21. 

 Swain has recently described this species and 

 discussed its generic position. 



Dimensions: Fig. 16: length 0.61 mm; height 

 0.27 mm. 



Occurrence: Black Creek only, localities G, J, 

 and K. U.S.N.M. 128962, 128963. 



Remarks : Specimens from the outcropping sec- 

 tions are generally smaller than the holotype de- 

 scribed by Swain from a well section, otherwise 

 they are judged to be conspecific. Average length 

 of the present specimens is ±0.60 mm. 



Genus Progonocythere Sylvester— Bradley, 



1948 



Progonocythere caswellensis Brown, n. sp. 



Plate 4, Figures 14, 15 



Carapace small, subquadrate in lateral view; 

 widest anterad, highest just posterad of median ; 

 dorsal margin straight; ventral margin slightly 

 concave medially ; anterior margin broadly round- 

 ed, finely spinose ventrally ; posterior margin less 



broadly rcunded, slightly extended medially, finely 

 spinose. 



Entire valve surface covered with high, narrow 

 square-sided ridges, vertically aligned and more 

 pronounced ventrally ; ridges on the anterior 

 third are slightly longer and roughly subparallel 

 to the anterior margin ; dorsad and posterad, the 

 ridges are more subdued. Closely spaced square- 

 sided ridges and deep interridge areas give the 

 valves a very distinct deeply reticulate appear- 

 ance, vertically aligned. 



Hinge of left valve with terminal elongate den- 

 ticulate sockets and a finely crenulate interter- 

 minal bar all located high on the marginal rim. 

 Hinge of right valve counterpart of the left. 



Dimensions : Holotype : length 0.63 mm ; height 

 0.31 mm; convexity 0.16 mm. 



Occurrence: Peedee only, localities A, C, and 

 F. U.S.N.M. 128964, 128965. 



Remarks: This species bears closest resem- 

 blance to Progonocythere hieroglyphica Swain 

 and Peterson from the Sundance formation of 

 Jurassic age. This is the first recorded occurrence 

 of the genus in the Cretaceous. 



Genus Cytheridea Bosquet, 1850 



Stephenson (1936) erected several subgenera 

 under the genus Cytheridea Bosquet. Among 

 these subgenera were Haplo cytheridea and Cli- 

 thro cytheridea which Stephenson, at a later date 

 (1946), raised to the rank of genera. The critical 

 point of distinction between Haplocytheridea and 

 Clithrocytheridea was defined as slight differences 

 in hingement. Cretaceous specimens of Haplocy- 

 theridea and Clithrocytheridea from North Caro- 

 lina exhibit hinge structure in which hingement 

 as defined for both Haplocytheridea and Clithro- 

 cytheridea is present in the same species. In addi- 

 tion, reversal of hingement, in which the normal 

 (?) dentition of a right valve appears in the left 

 valve, is commonly observed. Schmidt (1948) 

 commented on this mixed dentition in connection 

 with Cretaceous specimens. Swain (1952) and 

 Alexander (1933) have pointed out cases of re- 

 versal of hingement and valve overlap in Creta- 

 ceous Cytheridea. 



In this paper both Haplocytheridea and Cli- 

 throcytheridea are reduced in rank to subgenera 

 with the feeling that further revision will be nec- 

 essary as additional populations are studied. Spe- 

 cies in this paper are given as Cytheridea (Hap- 

 locytheridea) if they exhibit a prominent accom- 



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