46 



CHESTER OSTRACODES OF ILLINOIS 



Although not mentioned in the description, 

 the British form also seems to have an in- 

 flated area between the nodes and the ven- 

 ral margin as in the species shown here. 

 The smaller node is poorly developed. It 

 differs from H. grauifera (Ulrich) in the 

 lack of the frill, the presence of a spinose 

 margin with two very large spines, and in 

 the distinct retral swing. 



HoLLiNELLA RADiATA (Jones and Kirkby) 

 Plate 9, figures 42-44 



Beyrichia radiata Jones and Kirkby, 1886, Ann. 



Mag. Nat. Hist., ser. 5, vol. 18, p. 257, pi. 8, 



figs. 1, 2a, b. Carboniferous of Great Britain. 

 Beyrichia radiata cestriensis Ulrich, 1891, Jour. 



Cincinnati Soc. Nat. Hist., vol. 13, p. 204, 



pi. 14, figs. 4a, b. 

 Hollina radiata cestriensis. Ulrich and Bassler, 



1908, Proc. U. S. Nat. Mus., vol. 35, p. 315, 



pi. 42, figs. 19, 20. 

 Hollina radiata. Latham, 1933, Trans. Roy. Soc. 



Edinburgh, vol. 57, pt. 2, pp. 359, 360, fig. 8. 

 Hollina a'uonensis Latham, 1933, ibid., p. 360, 



fig. 9. 

 Hollinella cestriensis. Bassler and Kellett, 1935, 



Geol. Soc. Am., Spec. Paper 1, p. 332. 

 Hollinella radiata. Bassler and Kellett, 1935, 



ibid., p. 334. 

 Hollinella typica Morey, 1935, Jour. Paleontology, 



vol. 9, p. 479, pi. 54, fig. 19, Amsden forma- 

 tion. 

 Hollinella sp., Croneis and Funkhouser, 1938, 



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



p. 341, pi. 9, fig. 15, Clore formation. 

 Hollinella moreyi Croneis and Bristol, 1939, 



idem., vol. 34, p. 77, pi. 4, fig. 18, Menard 



formation. 



Carapace subrhomboidal, with moderate 

 retral swing; ends rounded, cardinal angles 

 obtuse ; hinge straight ; anterior node even 

 with or below hinge line and more than 

 twice diameter of posterior one ; sulcus deep, 

 narrow, located between nodes just behind 

 midpoint of shell ; surface coarsely punctate, 

 sparsely to thickly spinose, margins and 

 cardinal angles often carrying well-develop- 

 ed somewhat larger spines; frill wide, flar- 

 ing, occupying about three-fourths of free 

 margin, often quite variable in width and 

 m the angle of attachment to shell, some- 

 times turning sharply outward, sometimes 

 directed downward. 



Length, 1.34 mm; height, 0.78 mm. 



Glen Dean formation, locality 1, rare; 

 Vienna formation, locality 10, common; 

 Menard formation, locality 7, common ; 

 Clore formation, locality 26, rare; Kinkaid 

 formation, locality 5, common. 



The study of specimens from the Illinois 

 Chester, ranging from the Glen Dean to 

 the Kinkaid, and a close scrutiny of the pub- 

 lished species from comparable horizons 

 elsewhere, have convinced me that the vari- 

 able character of the minor details makes it 

 impossible to distinguish separate species 

 from these formations. The position of the 

 large node with reference to the dorsal 

 margin, the variations in surface markings, 

 and the changing character of the frill all 

 appear to be quite variable. 



Family Kirkbyidae Ulrich and Bassler 



Genus Discoidella Croneis and Gale 



DiscoiDELLA AMPLA Cooper, n. sp. 



Plate 9, figures 36-37 



Carapace very small, disc-shaped, outline 

 subcircular, thickest in dorso-central area; 

 very coarse reticulae in irregular rows sub- 

 parallel to venter, becoming larger and 

 more irregular in arrangement toward dor- 

 sum ; cardinal area short, wide, somewhat 

 depressed ; dorsal angles subequal. 



Length, 0.45 mm; height, 0.42 mm; 

 thickness, 0.25 mm. 



Renault formation, locality 9, rare. 



D. ampla differs from other described 

 species in the position of greatest thickness 

 located near the dorsum, its larger size, and 

 depressed cardinal area. 



' Genus KiRKBYA Jones 



KiRKBYA ELONGATA Cooper, n. sp. 

 Plate 10, figure 50 



Carapace elongate, narrow, with promin- 

 ent retral swing; hinge line straight in lat- 

 eral view except for small offset at each 

 end ; anterior shoulder prominent, posterior 

 faint ; inner frill narrow, upturned ; greatest 

 thickness well forward of and slightly above 

 center; posterior cardinal angle 90°, an- 

 terior angle acute ; surface markings not 

 preserved. 



Length, 0.87 mm; height, 0.37 mm. 



Paint Creek formation, locality 2, rare. 



KiRKBYA HUMEROSA Coopcr, n. Sp. 

 Plate 10, figures 47-49 



Carapace thick, elongate, hinge straight, 

 dorsal and lateral outlines asymmetrical; 

 anterior shoulder prominent, extending 

 slightly above hinge line; cardinal angles 



