64 



CHESTER OSTRACODES OF ILLINOIS 



Evidence for the association of these 

 peculiar Chester forms with Tetrasacculus 

 is furnished by the male specimen here 

 figured. Such features as the centro-ventral 

 and posterior lobes, lateral outline, dorsal 

 and ventral aspect in the male, and the 

 number and position of the brood pouches 

 in the female make this classification rather 

 certain. Work?na}iella of Croneis and Gale 

 seems indistinguishable from the male Tet- 

 j'dsac cuius. 



Family Youngiellidae Jones and Kirkby 



Genus Moorea Jones and Kirkby 



MooREA? CIRCINCTA Cooper, n. sp. 



Plate 14, figures 37-40 



Carapace ovate, subelliptical, ends round- 

 ed ; dorsum and venter very slightly con- 

 vex, almost straight; margins bounded by 

 low, narrow ridge parallel to dorsal and 

 ventral margins, subparallel to each end, 

 enclosing broad, gently convex or almost 

 flat area; sides parallel; overlap very slight 

 but continuous around free margins ; dorsum 

 channeled by depressed hinge, ending with 

 a notch at either end. 



Length, 0.52 mm; height, 0.28 mm; 

 thickness, 0.20 mm. 



Paint Creek formation, locality 2, rare. 



This species agrees very closely to the 

 generic description of Moorea, but is clas- 

 sified with this genus with some hesitation. 

 The encircling ridge of M.f circincta is es- 

 sentially in one plane while that of M. 

 obesa Jones and Kirkby and M. tenuis 

 Jones and Kirkby show, in the ventral view, 

 a distinct bending toward the line of articu- 

 lation. No adequate description of the 

 hinge is available for Moorea; the hinge 

 of the Paint Creek form is sansabelloid. 

 If this holds for all species, then a recon- 

 sideration of family affinities is necessary. 



Genus Moorites Coryell and Billings 



MooRiTES BREVis Cooper, n. sp. 



Plate 14, figure 43 



Carapace short ; retral swing slight ; dor- 

 sal and ventral margins somewhat convex; 

 valves thickened along entire free margin, 

 especially anteriorly and ventrally; surface 

 punctuate. 



Length, 0.47 mm; height, 0.27 mm. 



Vienna formation, locality 10, common. 



The form ratio of 1.9 shows that this 

 species is a shorter form than M. rhomboi- 

 dalis (Croneis and Gutke), which it closely 

 resembles in other respects. 



Moorites convexus Cooper, n. sp. 

 Plate 14, figures 32-33 



Carapace ovate, ends rounded, anterior 

 cardinal angle being more obtuse; dorsum 

 straight, venter nearly so, parallel to dor- 

 sum ; thickening of shell apparent only at 

 extremities ; surface shallowly pitted ; sides 

 distinctly convex; hinge somewhat chan- 

 neled. 



Length, 0.47 mm; height, 0.23 mm; 

 thickness, 0.20 mm. 



Paint Creek formation, locality 2, rare. 



M. convexus has the same lateral con- 

 figuration (and form ratio) as M. rhom- 

 boidalis (Croneis and Gutke), but the 

 latter lacks the convexity of the carapace 

 in dorsal view, and possesses a thickening 

 of the shell around the ventral margin. 



Moorites elongatus Cooper, n. sp. 

 Plate 14, figures 20-21 



Carapace elongate, dorsum and venter 

 straight, parallel; ends rounded, especially 

 posteriorly, with dorsal and ventral angles 

 essentially equal; antero-cardinal angle 

 prominent; surface smooth. 



Length, 0.43 mm; height, 0.18 mm; 

 thickness, 0.12 mm. 



Renault formation, locality 9, common ; 

 Paint Creek formation, locality 2, rare. 



This species differs from M. rhomboidalis 

 (Croneis and Gutke) and M. convexus 

 n. sp. in its relatively greater length (form 

 ratio 2.35). 



Moorites intermedius Cooper, n. sp. 

 Plate 14, figures 41-42 



Carapace elongate, with distinct retral 

 swing; sides slightly convex; ventral mar- 

 gin concave; dorsum straight; ends round- 

 ed ; valves thickened on ends and around 

 ventral angles, this thickness diminishing 

 to almost nothing at middle of ventral mar- 

 gin ; surface granulose or finely reticulate. 



Length, 0.47 mm ; height, 0.20 mm ; 

 thickness, 0.13 mm. 



Renault formation, locality 9, common. 



