58 



CHESTER OSTRACODES OF ILLINOIS 



overlap very slight around free margins ; 

 sinus indistinct, wide and shallow^, located 

 well forward of middle; greatest thickness 

 and height near posterior end, right valve 

 slightly higher than left ; greatest length 

 central ; surface smooth. 



Length, 0.89 mm; height, 0.51 mm; 

 thickness, 0.44 mm. 



Golconda formation, locality 19, com- 

 mon. 



Genus Perprimitia Croneis and Gutke 



Perprimitia Croneis and Gutke, 1938, Bull. Deni- 

 son Univ., Jour. Sci. Lab,, vol. 33, p. 257. 



This genus possesses, in addition to the 

 features described by Croneis and Gutke, 

 a well developed sansabelloid hinge line and 

 a forward swing to the valves. It is believed 

 that these features together with the dis- 

 tinct overlap and characteristic lobation 

 make this genus conform more closely to 

 the Kloedenellidae than to the Primitiidae. 

 The great variation in tumidity is thought 

 to be sexual although no males and females 

 of the same species have yet been designated, 

 nor has the reversal of valves, as in Sansa- 

 bella, been noted. 



Perprimitia elongata Cooper, n. sp. 

 Plate 12, figures 30-32 

 Carapace elongate ; dorsal margin 

 straight; end rounded; antero-dorsal angle 

 sharp; node and ventral lobe not sharply 

 differentiated but almost imperceptibly 

 joined together; spine short, located un- 

 usually far back from posterior end; over- 

 lap somewhat indistinct; greatest height 

 anterior ; greatest length and thickness cen- 

 tral. 



Length, 0.45 mm; height, 0.23 mm; 

 thickness, 0.17 mm. 



Paint Creek formation, locality 2, com- 

 mon. 



This species may be distinguished by its 

 unusual length, due to the relatively great 

 distance between the spine and the ventral 

 lobe. The figured specimen is a male. 



Perprimitia funkhouseri 



Croneis and Thurman 



Plate 12, figures 44-45 



Perprimitia funkhouseri Croneis and Thurman, 

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

 vol. 33, p. 304, pi. 7, figs. 18, 19, Kinkaid 

 formation. 



Jonesinaf tumida Croneis and Thurman, idem.,, 

 p. 305, pi. 7, fig. 11, Kinkaid formation. 



Ulrichia emarginata Ulrich, 1891, Jour. Cincin- 

 nati Soc. Nat. Hist., vol. 13, p. 203, pi. 12, 

 figs. lOa-c, Chester series. 



Length 0.60 mm; height, 0.37 mm; 

 thickness, 0.32 mm. 



Clore formation, locality 39, rare; 

 Kinkaid formation, locality 28, depth 628-33 

 feet, rare; locality 3, abudant. 



The examination of a score of more 

 specimens from a locality (No. 3) near that 

 which furnished the types J .f tumida shows 

 that the casts of P. funkhouseri quite often 

 do not show the spine on the posterior end 

 but the "largest node occupies complete 

 posterior portion of carapace, being so 

 swollen as to be almost uniformly convex." 

 Otherwise the specimens are in such close 

 agreement that I believe they are conspecific. 

 Ulrich's species from the Clore of Kentucky 

 is certainly a Perprimitia and very close to 

 F. funkhouseri. 



Perprimitia robusta Croneis and Gutke 

 Plate 12, figures 46-48 



Perprimitia robusta Croneis and Gutke, 1938, 

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

 p. 257, pi. 5, fig. 23, Renault formation. 



Perprimitia spinosa Croneis and Gutke, idem., 

 p. 258, pi. 5, fig. 28, Renault formation. 



Length, 0.67 mm; height, 0.38 mm; 

 thickness, 0.33 mm. 



Renault formation, locality 9, common; 

 Paint Creek formation, locality 2, rare; 

 Golconda formation, locality 17, rare. 



The sulcus of the holotype of P. spinosa 

 is matrix-filled and the small node anterior 

 to the pit is indistinguishable. For these 

 reasons and because the form ratios are the 

 same I consider these forms so nearly 

 identical as to be conspecific. 



Perprimitia sigynae 

 (Coryell and Johnson) 



Lokius sigynae Coryell and Johnson, 1939, Jour. 

 Paleontology, vol. 13, p. 216, pi. 26, figs. 6a-c, 

 Clore formation. 



Perprimitia tenera Cooper, n. sp. 

 Plate 12, figures 36-38 



Carapace small, subovate ; dorsal margin 

 straight, ends rounded, antero-dorsal angles 

 about equal; overlap inconspicuous around 

 free margin; spine prominent, extending 

 well above dorsum in lateral view; node 



