NO. 14-16. ,YEW PALEOZOIC OSTRACODA—ULRICH AND BASSLER. 159 



It is thought possible that this variety may indicate merely a sexual 

 phase of B. holl iaformis. Supposed female individuals of a number 

 of Silurian and Devonian species of Bei/rlchla are known, but in these 

 the tumidity is larger and much more sharply defined, and it occurs, 

 not on one of the ends, but always on the ventral side of the valves. 



Formation cuid locality. — Associated with, but apparently never so 

 abundant as, the typical form of the species in Kansas and Texas. 



Cotypes.—Q^t. No. 35630, U.S.N.M. 



Family KIRKBYID^E, new family. 



Genus KIRKBYA Jones. 



KIRKBYA PINGUIS, new species. 



Plate XI, figs. 13 to 15. 



Length 0.64 mm., height 0.37 mm., thickness 0.38 mm. 



Carapace rather suiall, thick, suboblong, ends blunt in edge views, 

 nearly equal and rounded in a side view; antero-cardinal angle obtuse, 

 the posterior angle quite indistinguishable, ventral margin gently con- 

 vex, the central portion nearly straight; dorsal outline straight in the 

 anterior half and slightly convex in the posterior half, the latter part 

 of the back being slightly impressed at the hinge line. Surface of 

 valves with a subcenti'ally situated, rather small, and only moderately 

 prominent node, and behind this, with a small sulcus intervening, two 

 less conspicuous nodes placed one above the other, the larger of the 

 two being near the post-cardinal angle. Free margins with a narrow 

 but well-defined fiat rim. Surface of test neatl}^ reticulated, with small 

 meshes. The diagnostic Kirkbyan "pit" is small and situated very 

 near the center of the valve on the ventral slope of the median node. 



This small ostracod is not very closely related to any described 

 species. A', oljloiiga clones and Kirkby and K. lindahll Ulrich are 

 probably the nearest, but both are considerably larger while the 

 valves of the former are without either nodes or a sulcus. 



Format Ion and locality. — Cottonwood shales, Smiles east of Cotton- 

 wood Falls. Kansas. 



Holotype.—OAt. No. 35629, U.S.N.M. 



KIRKBYA CENTRONOTA, new species. 



Plate XI, tigy. Ki, 17. 



Length of a large example 0.82 mm., height 0.50 mm., thickness 

 3.50 mm. 



Carapace oblong subquadrate, with thick flattened edges, a long, 

 straight back, and rather sharp cardinal angles, the posterior angle 

 :he less sharp of the two. Valves with a prominent large rounded 

 lode situated very near the middle of the dorsal half. On either side 

 )f this a smaller elevation surmounted by a thin curved \'ertical ridge 

 n old examples. The marginal ridge, which likewise is well devel- 



