50 



CHESTER OSTRACODES OF ILLINOIS 



ECTODEMITES COSTELLIFERUS 



(Croneis and Bristol) 

 Plate 9, figure 22 



Amphissites costellifera Croneis and Bristol, 1939, 

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

 p. 80, pi. 4, fig. 5, Menard formation. 



Amphissites decipiens Croneis and Bristol, 1939, 

 idem., p. 81, pi. 4, fig. 4, Menard formation. 



Length, 1.0 mm; height, 0.55 mm. 



Golconda formation, locality 8, rare; 

 Vienna formation, locality 10, rare; Men- 

 ard formation, locality 28, rare. 



ECTODEMITES ELONGATUS Cooper, H. sp. 

 Plate 9, figures 24-25 



Carapace long, high, greatest thickness 

 almost central ; anterior and central swell- 

 ings joined by very low saddle, the former 

 but slightly elevated above hinge line, end- 

 ing at inner carina; pit well below center, 

 elongated horizontally, deep; reticulations 

 polygonal to ovate, regularly disposed with 

 reference to carina; inner carina merges 

 with line between two adjacent rows of 

 reticulations about half way between pit and 

 posterior end. 



Length, 0.79 mm; height, 0.47 mm; 

 thickness, 0.42 mm. 



Kinkaid formation, locality 6, rare. 



ECTODEMITES MAGNIRETICULATUS 



Cooper, n. sp. 

 Plate 9, figures 16-17 



Carapace subrectangular ; dorsum 

 straight, venter slightly concave, subparal- 

 lel to dorsum, ends rounded ; retral swing 

 slight ; surface very coarsely reticulate, 

 smoothly convex, without nodes or should- 

 ers; pit slightly below center, equidistant 

 from ends; hinge straight, slightly de- 

 pressed ; one very faint false keel closely 

 parallels venter. 



Length, 0.74 mm; height, 0.38 mm; 

 thickness, 0.31 mm. 



Paint Creek formation, locality 2, rare. 



ECTODEMITES cf. MONOMASTADIS 



(Coryell and Sohn) 



Plate 9, figure 35 



Amphissites monomastadis Coryell and Sohn, 

 1938, Jour. Paleontology, vol. 12, p. 602, 

 pi. 69, figs. 10a, b, Reynolds limestone. 



Length, 0.86 mm; height, 0.49 mm. 



Menard formation, locality 30, rare. 



EcTODEMiTES OBESUS (Croneis and Gale) 



Plate 9, figures 28-29 



Amphissites ohesus Croneis and Gale, 1938, Deni- 

 son Univ. Bull., Jour. Sci. Lab., vol. 33, p. 

 270, figs. 2, 3, Golconda formation. 



Length, 0,78 mm; height, 0.42 mm; 

 thickness, 0.44 mm. 



Renault formation, locality 12, common ; 

 Paint Creek formation, locality 2, rare; 

 Golconda formation, locality 28, depth 

 1068-69 feet, rare. 



ECTODEMITES OBLONGUS 



(Jones and Kirkby) 

 Plate 9, figure 23 



Kirkhya ohlonga Jones and Kirkby, 1885, Ann. 



Mag. Nat. Hist., ser. 5, vol. 15, p. 181, pi. 3, 



figs. 6a, b. Carboniferous of Great Britain. 



Ulrich, 1891, Jour. Cincinnati Soc. Nat. 



Hist., vol. 13, p. 206. pi. 18, figs. 4, 5, Chester 



series. 

 Amphissites ohlonga. Roth, 1929, Wagner Free 



Inst. Sci., Pub., vol. 1, p. 8. 



Length, 0.86 mm; height, 0.47 mm. 

 Vienna formation, locality 10, common. 



ECTODEMITES PARVUS Coopcr, n. sp. 

 Plate 9, figures 30-31 



Carapace small, elongate, somewhat 

 rectangular in lateral view, surface finely 

 reticulate; false keels poorly developed, 

 inner one almost indistinguishable; dorsal 

 area considerably flattened, but rising 

 posteriorly considerably above remainder of 

 hinge line ; median and anterior swellings 

 separated by fairly prominent saddle; pit 

 oval, very distinct. 



Length, 0.71 mm; height, 0.28 mm; 

 thickness, 0.32 mm, 



Menard formation, locality 7, common. 



This species closely approaches Am- 

 phissites but lacks the carinal development 

 of that genus, especially in the dorsal area. 



ECTODEMITES PLANUS Cooper, n. sp. 

 Plate 9, figures 40-41 



Carapace elongate, subrectangular in out- 

 line, lenticular in dorsal view ; central 

 swelling does not interrupt the regular line 

 of curvature; carina indistinct; surface 

 reticulae coarse and concentric ; anterior 

 shoulder absent ; cardinal angles well round- 

 ed ; pit located well below center, equidis- 

 tant from the extermities of shell. 



