Genus Clithrocytheridea Stephenson, 1936 



Clithrocy theridea halif axensis Swain and Brown, 

 n. sp. 



Plate 2, Figures 5a-c 

 Text Figure 6a 



Shell subovate in side view, highest anterior to 

 middle ; dorsal margin moderately convex, sloping 

 more steeply in front of than behind position of 

 greatest height; ventral margin gently convex; 

 anterior margin broadly and uniformly rounded; 

 posterior margin more narrowly rounded, extended 

 below especially in right valve, subtruncate above. 

 Left valve larger than right; complete carapace 

 not seen, but judged from the selvage, left valve 

 overlaps and extends beyond edge of right, except 

 posteroventrally. 



A shallow anteromedian sulcus extends from 

 near dorsal margin to midheight; surface pos- 

 terior to sulcus is inflated in both valves, and in 

 right valve a low elevation of surface occurs an- 

 terior to sulcus. Surface of valves, except for 

 smooth marginal zone, is coarsely and densely 

 pitted. 



Hinge of left valve consists of an elongate den- 

 ticulate socket containing about six cross-bars, an 

 interterminal weakly crenulate bar dorsal to which 

 is an accommodation groove, and a posterior, 

 somewhat smaller and narrower, denticulate soc- 

 ket. Hinge of right valve has denticulate terminal 

 sockets, between which the interterminal area is 

 depressed, faintly grooved, and has a very weak 

 accommodation groove. Inner lamellae not broad, 

 line of concrescence and inner margin separated 

 anteriorly and posteriorly ; radical canals number 

 about 12 anteriorly, fewer posteriorly, and are 

 irregularly spaced. Muscle scar a somewhat anter- 

 omedian vertical row of four spots and two addi- 

 tional spots anterior to ends of main row. 



Length of holotype left valve 0.65 mm, height 

 0.40 mm, convexity of valve 0.20 mm. 



Relationships. — The new species is generally 

 similar to the Eocene C. garretti (Howe and 

 Chambers) (1935, p. 14) in shape, hingement 

 and surface pitting. It is more ovate and less tri- 

 angular than C. garretti and is considerably more 

 ovate and with much coarser surface pitting than 

 other described Cretaceous species. Clithrocyth- 

 eridea decumana Triebel (1938, p. 492) from the 

 Aptian of Germany resembles the new species in 

 general shape and coarsely pitted surface, but is 

 more pointed posteriorly and has a small postero- 

 ventral spine. 



Occurrence. — The species is rare in the lower 



Cretaceous in the Caledonia Prison Farm water 

 well T-2, Halifax County, North Carolina, from 

 depths of 166-176 feet and 241-246 feet; and in 

 the T-4 water well from 151-156 feet; probably 

 Washita (Albian) in age. 



Genus Dolocytheridea Triebel, 1938 



Dolocytheridea? caledonensis Swain and Brown, 

 n. sp. 



Plate 2, Figure 6 



Shell elongate, almond-shaped in side view, 

 highest medially, dorsal margin moderately and 

 nearly uniformly convex; ventral margin gently 

 convex, slightly sinuous anteriorly; anterior mar- 

 gin broadly curved, slightly extended below; pos- 

 terior margin more narrowly rounded, extended 

 medially. Left valve appreciably larger than right, 

 overlapping and extending beyond right strongly 

 along dorsal and ventral, but less strongly along 

 terminal margins. Valves rather strongly convex, 

 with greatest convexity posteromedian in posi- 

 tion. Surface nearly smooth, except for a few scat- 

 tered pits. 



Hinge of right valve consists of terminal denti- 

 culate and elongate toothlike elevations and an 

 interterminal faintly crenulate groove; hinge of 

 left valve, correspondingly, is made up of denticu- 

 late terminal sockets and an interterminal crenu- 

 late bar. Muscle scars an anteromedian vertical 

 row of four spots and two more anterior spots 

 lying opposite each end of main group. 



Inner lamellae of moderate width; line of con- 

 crescence and inner margin separated terminally; 

 radial canals numerous, occupying different levels 

 along marginal zone and emerging at different 

 horizons along outer margin. Normal canals num- 

 erous, widely but uniformly spaced. 



Length of holotype shell 0.73 mm, height 0.43 

 mm, convexity 0.37 mm. 



Relationships. — This species is very closely sim- 

 ilar to "Ciftheridea amygdaloides" Alexander 

 (1929, p. 69) from the Kiamichi of Texas which 

 according to Howe and Laurencich (1958, p. 273) 

 is not Cy there amygdaloides (Cornuel) ( = Do- 

 locytheridea hilseana (Roemer) ) but is probably 

 a Dolocytheridea. Alexander's species is not as 

 elongate as the present form and is here consid- 

 ered a separate species. 



Occurrence. — Rare in Caledonia Prison Farm 

 water well T-4, Halifax County, North Carolina, 

 Lower Cretaceous of early ? Albian (late Fred- 

 ericksburg) age. 



22 



