42 



CHESTER OSTRACODES OF ILLINOIS 



Glyptopleura tyri 



(Coryell and Johnson) 



Plate 8, figures 10-11 



Glypioplcuritcs tyri Coryell and Johnson, 1939, 

 Jour. Paleontology, vol. 13, p. 219, pi. 26. figs. 

 lOa-c, Clore formation. 



Length, 0.67 mm; height, 0.35 mm; 

 thickness, 0.29 mm. 



Clore formation, locality 27, rare. 



Glyptopleura varians 



Croneis and Funkhouser 



Plate 8, figures 15-17 



Glyptopleura varians Croneis and Funkhouser, 



1938, Bull. Denison Univ., Jour. Sci. Lab., 

 vol. 33, p. 355, pi. 10, figs. 5, 6, Clore forma- 

 tion. 



Glyptopleura freyjae Coryell and Johnson, 1939, 

 Jour. Paleontology, vol. 13, p. 219, pi. 26, fig. 

 17, Clore formation. 



Ceratopleurina mimiri? Coryell and Johnson, 



1939, idem., p. 221, pi. 26, figs. 9a, b, Clore 

 formation. 



Length, 0.78 mm; height, 0.46 mm; 

 thickness, 0.33 mm. 



Menard formation, locality 20, rare; 

 Clore formation, locality 27, rare; Kinkaid 

 formation, locality 3, common. 



Glyptopleura venosa (Ulrich) 



Plate 8, figures 19-21 



Kirkhya 'uenosa Ulrich, 1891, Jour. Cincinnati 



Soc. Nat. Hist., vol. 13, p. 208, pi. 18, figs. 



3a, b, Glen Dean formation. 

 Glyptopleura venosa. Coryell and Brackmier, 



1931, Am. Midland Nat., vol. 12, p. 516, pi. 



2, fig. 5. 



Carapace ovate, nearly symmetrical, 

 greatest height slightly in front of center ; 

 hinge straight; ribs irregularly curved, 

 anastomosing; surface reticulate; border of 

 free margins flat to slightly depressed ; 

 greatest thickness anterior. 



Length, 0.89 mm; height, 0.53 mm; 

 thickness, 0.53 mm. 



Kinkaid formation, locality 3, common. 



This Kinkaid form is identical v^^ith that 

 described by Ulrich from the Glen Dean of 

 Kentucky in shape, markings, and size; the 

 latter is erroneously stated in the original 

 description, but Ulrich's figure shows that 

 the holotype is almost exactly the same size 

 as the Kinkaid specimen. 



Genus Glyptopleurina Coryell 



Glyptopleurina Coryell, 1928, Jour. Paleontology, 

 vol. 2, p. 381. 



Idiomorphina Croneis and Gale, 1938, Bull, Deni- 

 son Univ., Jour. Sci. Lab., vol. 33, p. 284. 



Coryell differentiated Glyptopleurina 

 from other Glyptopleuridae by the presence 

 of nodes and flange in addition to the inos- 

 culating costae. The subsequent descriptions 

 of several species from the Chester have 

 shown that the flange is an extremely vari- 

 able character, in some species being al- 

 most inconspicuous around the entire free 

 margin, and well developed only at the 

 ends of the carapace. 



Idiomorphina was described as being more 

 bulbous posteriorly than Glyptopleurina 

 and as possessing a split anterior lobe. How- 

 ever, in their description of G. bulbosa, 

 Croneis and Gale list the split lobe as a 

 specific character. The genotype /. insignia 

 is a single right valve and since the marginal 

 development of Glyptopleurina is somewhat 

 variable, this feature therefore is of doubt 

 ful generic value. It is suggested that the 

 three described species of Idiomorphina are 

 all females, which would explain the obe 

 sity of the posterior end. 



Some species of Glyptopleurina bear a 

 general resemblance to Geffenina and Geff- 

 enites, except that the latter genera do not 

 possess the curved rib joining the dorsal 

 nodes, nor is the marginal lobe so sharply 

 defined as in Glyptopleurina. The orienta- 

 tion of this family has been reversed to con- 

 form to more recent ideas concerning 

 ostracode orientation, which makes the right 

 valve the larger and the overlapping one. 

 This puts the position of the greatest thick- 

 ness and ventral truncation posterior, and 

 the obtuse cardinal angle anterior (Geis, 

 1932, pp. 150-155). 



Glyptopleurina flexuosa Cooper, n. sp. 

 Plate 8, figures 25-27 



Carapace large, elongate, ovate, hinge 

 straight, ends rounded; venter slightly 

 convex, wedge-shaped in dorsal view; node 

 slightly elongate vertically; ventral margin 

 joined to narrow rib which turns abruptly 

 upward and across shell where it joins an- 

 terior inflation about midway between 

 dorsum and venter; rib distinctly con- 

 cave downw^ard ; hinge straight, channelled, 

 with distinct notch at posterior end; mar- 

 ginal ridge broad and close to ventral and 

 posterior margins, merging into inflation on 

 opposite end. 



