6 PALAEONTOLOGY OF KENTUCKY. 



opening is due to wear and rubbing in its fossil condition. The internal 

 structure is destroyed, and only the outline or general form preserved. The 

 central body measures six inches in diameter, while the circle, formed by the 

 tops of the tubes, has a diameter of nine inches. 



Formation and. Locality. This interesting fossil is limited to one locality; it is found in the lower 

 strata of the Cincinnati or Hudson Kiver group, at Bright's Mill, on Benson Creek, a few miles west of 

 Frankfort, Ky., where, altogether, not more than about a dozen fcir specimens have been found, while 

 ractional specimens are more numerous. 



MOLLUSCA. 



BRYOZOA. 

 Genus Ptilodictya. Lonsdaie. 



Ptilodictya, Lonsdaie. Murch. Sil. Syst. 1839. 

 Etymology : ptilon, a wing ; dictyon, a net. 

 The correct orthography would be Ptilodictyon. 



Fronds simple or branched, springing from a pointed or wedge-shaped, sub- 

 solid, and finely striated base or articulating process, which fitted loosely in 

 the socket of the expanded and firmly attached base. The free portion of the 

 zoarium is two-edged, with the transverse or cross section acutely elliptical, 

 with the surface either smooth, montiferous, or marked by transverse ridges, 

 and composed of two equal but distinct sides ; each side is provided with a 

 delicate epithacal membrane, from which the cells rise to open on the two 

 opposite faces of the frond. Cells quadrate, rhomboidal, or hexagonal, and 

 arranged in longitudinal series, or in a quincuncial manner ; pseudo-septa are 

 frequently present ; the walls are pierced in many species by connecting fora- 

 mina. The interstitial cells are usually absent ; but in the nodose species the 

 summits of the monticules are often occupied by smaller cells than the aver- 

 age. In the robust species the tubes are crossed by diaphragms placed upon 

 the same level in contiguous tubes. 



Ptilodictya hilli. JAMES. 



Plate XXX V., figures 1, 2, 4 and 5. 

 Ptilodictya hilli, James. Cin. Journ. of Nat. Hist., Vol. V., pt. 3, plate 7, figure 7., no descpt. 1882. 



Zoarium digitate, the number of prongs not known ; the specimen before me 

 shows one complete branch, which deflects from the original stem, just above 

 the wedge-shaped articulating process, out of the sharp edge, and extending 

 in the same plane with the main stem. On one of the broad sides of the 

 main stem, and in its center line, are two protuberances, the one opposite 



