The Rogers Gap Fauna of Central Kentucky 135 



20 — Protozyga obsoleta, sp. nov. (Plate II, Figs. lOA, B) — 

 The typical forms of this species can be described most briefly 

 by stating that they look like specimens of Zygospira recurvi- 

 rostra in which the radiating plications have failed to appear, or 

 in which these radiating plications are barely indicated. Since 

 some of the specimens preserve fine concentric markings, it seems 

 incredible that any process of exfoliation could have left any speci- 

 mens of Zygospira with surfaces sufficiently smooth to be mistaken 

 for shells in which plications were absent or faint. On the other 

 hand, associated with these smooth individuals, in the same layers, 

 there are others in which the degree of plication is much more 

 pronounced, and which may eventually turn out to belong to 

 other species ; however, for the present, these more strongly pli- 

 cated forms are correlated with the typical smooth ones, since 

 the plications do not extend back as far as the beak, but are dis- 

 tinct only along the anterior half of the shell. In size and num- 

 ber these plications resemble those of Zygospira. The pedicel 

 valve is flattened along a narrow, obscure elevation medially, as 

 in Zygospira^ but the depression of the brachial valve does not 

 extend as far toward the beak, and along the junction of the 

 valves, laterally, the shell, in mature forms, is less angular. The 

 largest specimens seen do not exceed 9 mm. in width. The refer- 

 ence to Protozyga is only provisional. The illustrations of Proto- 

 z\ga e.vigua indicate shells wider posteriorly, with a more angu- 

 late outline, while those of Protozyga obsoleta are more rounded, 

 and widest near the middle. Forms of this kind, associated with 

 Orthorhynchiila, have long been known from the railroad cut about 

 two miles south of ^Nlillersburg, a short distance above track level, 

 north of an overhead bridge. Columnaria is abundant in the under- 

 lying layers. The horizon is in the lower part of the Millersburg 

 member of the Cynthiana formation. Recently my attention was 

 again attracted to these brachiopoda by Dr. E. O. Ulrich. About 

 50 specimens were collected, varying from forms quite smooth to 

 those in which the plications are conspicuous. Eventually it will 

 be possible to work out the brachidium and thus to determine the 

 affinity of the various forms with accuracy. Protozyga exigtta is 

 figured on plate o-i of the Paleontolog}' of New York, volume VIII. 



20 



