BARIDIIDAE 



27 



Carapace ovate; overlap around entire 

 margin, especially prominent along antero- 

 dorsal margin; postero-dorsal slope short 

 and straight ; ventral margin straight in cen- 

 tral portion; beak of medium length and 

 located below median line; curved ridges 

 low and close set, providing a broad area 

 between the anterior rib and the end of 

 the shell. 



Length, 0.77 mm; height, 0.43 mm; 

 thickness, 0.33 mm. 



Menard formation, locality 7, common; 

 Kinkaid formation, locality 5, abundant. 



Bairdiolites bulbosus 

 Croneis and Bristol 

 Plate 2, figures 19-20 

 Bairdiolites bulbosus Croneis and Bristol, 1939, 

 Bull. Denison Univ., Jour. Sci. Lab., vol. 34, 

 p. 95, pi. 3, figs. 14-15, Menard formation. 

 Bairdiolites emarginatus Croneis and Bristol, 

 1939, idem., p. 96, pi. 3, figs. 12, 13, Menard 

 formation. 



Length, 0.80 mm; height, 0.47 mm; 

 thickness, 0.31 mm. 



Golconda formation, locality 17, abun- 

 dant; Glen Dean formation, locality 1, rare ; 

 Vienna formation, locality 10, rare; Menard 

 formation, locality 20, common; Clore 

 formation, locality 26, common. 



Bairdiolites crassus Cooper, n. sp. 

 Plate 2, figures 29-30 



Carapace short and thick ; greatest height 

 almost central; overlap prominent around 

 entire margin, venter slightly curved, dor- 

 sal margin rounded, anterior and posterior 

 dorsal slopes fairly straight; postero-dorsal 

 slope unusually steep (ca. 55°) ; anterior 

 end rounded ; beak slightly below center 

 line; greatest height central; curved ridges, 

 if extended, would form a very short ellipse ; 

 hinge depressed, postero-central ; articula- 

 tion in dorsal view slightly curved. 



Length, 0.82 mm; height, 0.50 mm; 

 thickness, 0.26 mm. 



Clore formation, locality 28, abundant. 



Bairdiolites fornicatus Cooper, n. sp. 

 Plate 2, figures 27-28 

 Carapace small and very short; overlap 

 prominent except on antero- and postero- 

 ventral slopes; in lateral view articulation 

 above extremities forms high arch or curve, 

 which in most species is bounded by three 

 nearly straight lines; beak and anterior ex- 



tremity very low; venter straight only in 

 central third; dorsal articulation almost 

 straight. 



Length, 0.75 mm; height, 0.47 mm; 

 thickness, 0.29 mm. 



Menard formation, locality 15, common. 



This species may be distinguished by the 

 arch-like margin above the extremities 

 which occupy an extremely low position. 



Bairdiolites ovatus 



Croneis and Funkhouser 



Plate 2, figures 21-22 



Bairdiolites o'uatus Croneis and Funkhouser, 1938, 



Bull. Denison Univ., Jour. Sci. Lab., vol. 33, 



p. 357, pi. 9, figs. 13-14, Clore formation. 



Length, 0.73 mm; height, 0.46 mm; 

 thickness, 0.35 mm. 



Kinkaid formation, locality 5. 



The holotype from the Clore formation 

 has been so deeply corroded that the ribs 

 have almost disappeared from both valves. 

 This Kinkaid specimen, while slightly larg- 

 er than the type, agrees closely in outline 

 and general shape, the form ratio being 

 identical. 



Bairdiolites procerus Cooper, n. sp. 



Plate 2, figures 39-40 



Carapace ovate, rather high, with prom- 

 inent overlap around entire margin ; antero- 

 and postero-dorsal slopes straight, the latter 

 about 60°; dorsal margin of left valve 

 arched, that of right valve almost straight, 

 so that upper margin is bounded by three 

 almost straight lines ; lower margins curved ; 

 beak short and low, less than one-fourth 

 of height above venter ; curved ridges prom- 

 inent and close-set and would, if extended 

 to form a closed figure, result in a circle 

 (in more elongate species the extended 

 ridges would form ellipses) ; hinge de- 

 pressed ; surface slightly pitted. 



Length, 0.80 mm; height, 0.49 mm; 

 thickness, 0.35 mm. 



Kinkaid formation, locality 6, common. 



Bairdiolites tenuis Cooper, n. sp. 

 Plate 2, figures 37-38 

 Carapace very long, somewhat thin, ends 

 pointed; centro-dorsal area flat and sides 

 almost parallel; each end tapers to a long, 

 thin point; overlap greatest along venter, 

 w^hich is almost straight, and prominent on 

 the antero- and postero-dorsal slopes; the 

 latter being about 40° from the horizontal; 



