spurs from median ridge. A curved ridge extends 

 ventrally and posteriorly from eye tubercle, a me- 

 dian narrow ridge extends from a position ven- 

 trad of eye tubercle, backward and slightly up- 

 ward, to a point ventral to posterocardinal angle, 

 behind which, posterior end of shell is compressed ; 

 short spurs project at right angles from both 

 flanks of median ridge to join, as low ridges, with 

 spurs from dorsal and inner ventral ridges; two 

 ventral submarginal ridges are slightly shorter 

 than median ridge but are subparallel to it ; inner 

 ventral ridge highest posteriorly and joins end of 

 outer ridge with a cross-bar ; both ridges die out 

 gradually anteriorly and have several low con- 

 necting cross-bars between them. Internal fea- 

 tures not observed. 



Length of holotype shell 0.56 mm, height 0.30 

 mm, convexity 0.26 mm. 



Relationships. — The species is similar to C. 

 worthensis Alexander (1929, p. 92) from the 

 Washita Group of northern Texas in general shape 

 and ornamentation, including the double ventral 

 ridge, but has lower and broader surface ridges. 

 C. quadrialira Swain (1952, p. 84) from beds of 

 Eutaw ( ?) or Black Creek ( ?) age of North Caro- 

 lina also have similar surface ornamentation in- 

 cluding two ventral ridges but is more pointed 

 posteriorly and the surface ridges are broader. 



Occurrence. — Early Cretaceous, probably of 

 Washita (Albian) age, Greenville City well, Pitt 

 County, North Carolina, composite sample from 

 608-754 feet. 



Cythereis sp. aff . C. glabrella Triebel 

 Plate 3, Figure 5 



Right valve subquadrate in side view ; dorsal 

 margin sinuous due to extension of marginal 

 ridge; cardinal angles broadly and gently obtuse, 

 the anterior less wide than the posterior, ventral 

 margin gently convex; anterior margin broadly 

 rounded, somewhat extended below; bearing a 

 few small spines ventrally. Posterior margin acu- 

 minate, strongly extended medially, concave 

 above. Valve compressed, most convex postero- 

 medially, posterior fourth strongly compressed. 



Anterior margin provided with a narrow, 

 strongly elevated rim that continues uninterrupt- 

 ed along ventral margin but widens posteriorly to 

 a rounded node at place of termination about 

 one-third from posterior end ; anteriorly, outer 

 side of rim bears a few small spines, ventral out- 



er portion has several thick spurs that extend ob- 

 liquely backward and fuse to form a short sub- 

 sidiary ridge and enclose a series of curved pits; 

 and inner ventral slope has five or more short 

 spurs projecting from it. Dorsal margin bears a 

 sinuous, rather broad round-crested ridge that 

 extends from lucid eye tubercle to about one- 

 fourth from posterior end where it bends slightly 

 toward venter and terminates; posterior margin 

 also provided with a narrow, distinct, but low 

 marginal rim that has several low nodes each of 

 which represents a point of emergence of a radial 

 canal. Median longitudinal ridge broad, consisting 

 of an elongate swollen anteromedian nodelike ele- 

 ment and a posterior narrower element separated 

 from the other by a low saddle. Surface between 

 ridges is smooth. 



Hinge of right valve consists of an anterior 

 high pointed tooth, notched on its anterior slope 

 and a deep pit anteroventral to it, a posteriorly 

 adjacent deep rounded socket, a long interter- 

 minal, very weakly denticulate groove, and a pos- 

 terior high pointed tooth which has a few weak 

 notches on its anterior side. Free margins of valve 

 bear a narrow selvage ridge, and antero-mid- 

 ventrally a prominent selvage apophysis. Inner 

 lamellae moderately broad, line of concrescence 

 and inner margin coincide ; about 12 radial canals 

 anteriorly, and about 7 posteriorly, some are bifur- 

 cate outward; also, dorsal and ventral marginal 

 zones each have ten or more radial canals of vari- 

 able length. Muscle scar consists of a small com- 

 pact group of four elongate spots lying on anterior 

 slope of inner depression representing antero- 

 median node, and an additional more anterior 

 spot. 



Length of figured right valve 0.65 mm, height 

 0.33 mm, convexity of valve 0.20 mm. 



Remarks. — This shell is similar in shape and 

 general disposition and character of surface orna- 

 mentation to the group of Cythereis haivleyi Alex- 

 ander (1929, p. 95) and C. "nuda" Alexander 

 (1929, p. 91) from the Albian of Texas, but is 

 not pitted as is C. hawleyi and has different dor- 

 sal and ventral ridges from C. "nuda." C. glabrel- 

 la Triebel (1940) from the Albian of Germany 

 has shape and surface ridges generally like the 

 present species but does not have the short sub- 

 marginal spurs extending inward as does our 

 form. Veenia paratriplicata (Swain) (1952, p. 

 85) from the Upper Cretaceous of North Caro- 

 lina is similar to the present specimens in surface 



30 



