NO. i44(!. NEW PALEOZOIC OSTRACODA—VLRICH AND BAS8LER. 161 



study before a definite generic arrangement is attempted. Specifically, 

 O. ? haworthl is distinguished by the ventral wing-like prominence. 



Formation and locality. — Cottonwood shales, 2 miles east of Cotton- 

 wood Falls, Kansas. 



Holotype.—OAfi. No. 35658, U.S.N.M. 



Family BAIRDIID^. 



Genus BAIRDIA McCoy. 



BAIRDIA BEEDEI, new species. 



Plate XI, figs. 19, 20. 



Length 1.22 mm., height 0.75 mm., thickness 0.52 mm. Carapace 

 thick, short, subrhomboidal in outline, lanceolate in edge views, the 

 point of greatest thickness being near the middle; overlapping dorsal 

 edge of left valve thick, the ventral overlap also rather wide; poste- 

 rior extremity bluntly acuminate, the dorsal half of the outline nearly 

 sti'aight in the left valve and barely concave in the right valve, the 

 lower half arching broadly into the ventral margin; anterior extremity 

 less acuminate than the posterior, the outline being rounded in the 

 lower half, nearly straight in the upper half, and abruptly bent about 

 the mid-height. Valves unequal, the left much the larger, and the 

 middle partof its dorsal outline distinctly convex, while the correspond- 

 ing part of the right valve is sufliciently straightened to form obtuse 

 angles at the ends of the hinge. Surface of both valves evenly convex 

 and smooth. 



This species agrees better with B. cestriensis Ulrich than with any 

 other known to the writers. The principal difference lies in the shape 

 of the posterior end, this being longer and the upper half of its outline 

 straighter. Other differences are found in the greater dorsal overlap, 

 in the more curved ventral edge, and in the more uniformly curved 

 (lanceolate) outline in edge views. In young examples of the two 

 species these differences, however, are less readily apparent than in 

 fully developed specimens. B. plehe ia McCo y , which of the European 

 species is perhaps the nearest, is distinguished at once by its propor- 

 tionally greater length. 



The writers have a large number of specimens of Bairdia, appar- 

 ently representing six or seven species, procured mainly from Upper 

 Carboniferous rocks in the Mississippi Valley and Texas. Although 

 these have not yet been subjected to critical study, it is believed that 

 B. heedei occurs in some of the lots. However, pending careful com- 

 parisons, it would be unwise to attempt giving either the stratigraphic 

 or the geographic distribution of the species. 



Formation, and locality. — Cottonwood shales, 2 miles east of Cotton- 

 wood Falls, Kansas. 



Holotyjje.—i^At. No. 35634, U.S.N.M. 

 I' Proc. N. M. vol. XXX— 06 11 



