NO. i44(i. NEW PALEOZOIC OSTRACODA—VLRIt'H AND BASSLEU. 157 



opsis. The former condition is regarded as the more likely to prove 

 true. 



Unless it is the same as White and 8t. John's BeyricMa factoidea^ 

 which the writers have so far failed to identify, none of the known 

 American species are sufficiently like B.f emaciata to be easih^ mis- 

 taken for it. It is quite distinct also from all of the British species 

 described b}^ Jones and Kirkby. 



Formation and locality. — Yellow shales in the Wreford limestone, 

 6 miles west of Reece, Kansas. 



Holotype.—Q^i. No. 35632, U.S.N.M. 



Genus BEYRICHIELLA 'ones and Kirkby. 



BEYRICHIELLA GREGARIA, new species. 



Plate XI, fig. 18. 



Length 0.95 mm., height 0.58 mm. 



Valves subelliptical in outline, the hinge line nearly straight and 

 equaling in length about four-fifths of the longest diameter of the 

 carapace, the cardinal extremities rather obtusely angular, the two 

 ends subequal and rounding regularly into the ventral margin. The 

 latter part of the outline varies in different specimens, being dis- 

 tinctly convex in some (as in the figured example) and quite straight 

 in the middle third in others. P^xcept the portion of the main verti- 

 cal sulcus, which is well marked and located a little behind the center 

 of the dorsal half, the surface markings exhibit considerable variation. 

 The sulcus may be narrow with a broad swelling on either side, as in 

 the Hgured specimen, or it may be wider, the increase being at the 

 expense of the smaller (posterior) swelling. In the former case the 

 posterior lobe is commonly divided medialh^ by a faint vertical sulcus, 

 the two sulci and two intervening nodes giving an appearance that 

 reminds us of the Silurian genus Klcedenla. The large anterior lobe 

 rises abruptly from the median sulcus and is always the most promi- 

 nent part of the valve. Usually a small spine, occasionalh- of larger 

 size than in the tigure, rises from the antero-dorsal slope, while a 

 faint vertical sulcus is sometimes distinguishable just behind, the spine. 

 A large, ill-detined, longitudinal swelling generally occupies the lower 

 middle part of the valves, while beneath this a more or less obscure 

 depression sets off a ventral marginal flattening or flange. This mar- 

 ginal flange increases in width with age, young examples which then 

 expose the denticulated contact edge of the A^alve, being without it. 

 Although entire specimens have not been seen, the characters of the 

 separated valves leave no doubt that the left valve is the larger and 

 o verlaps the ventral edge of the right. 



No American species with which this might be confused has been 

 described. Compared with British species onh' Beyrlchiaf arcuata 

 (Bean), as figured bj^ Jones and Kirkby, seems near enough to require 



