BRYOZOA. 625 



much thickened near the base, rapidly tapering upward. In the 

 upper half of the frond the midrib is usually less than one-third 

 stronger than the branches, the latter being about 0.3 mm. 

 wide. Here the branches are lax, flexuous, and bifurcate rathej 

 frequently, a feature of very unusual occurrence among species 

 of the genus. 



Reverse. Branches and midrib moderately convex and finely 

 striated. Midrib slightly flexuous, tapering upward, giving off 

 on each side about nine branches, at an angle of near 45, in 

 1 cm. Branches connected by slender dissepiments forming 

 comparatively large irregular feuestrules, of which about four 

 follow each other in 5 mm. 



Obverse. Midrib and branches subcarinate, the rounded keel, 

 over the basal half of the zoarium, with closely arranged small 

 nodes. Over the outer half the keel is somewhat sharper, the 

 nodes less distinct, and, perhaps, wanting. Zooecia apertures 

 sub-oval, iu two ranges, about their diameter apart, sixteen or 

 seventeen in 5 mm.; with moderate peristome. 



The characters of the basal portion of the frond mentioned in 

 the above description have been derived from the central speci- 

 men of fig. 10. It is possible that this specimen may not be- 

 long to the same species as the other two represented in the 

 figure. It shows the obverse side, but most of the zooecia aper- 

 tures are closed by a striated deposit, so that I could not 

 satisfy myself in determining their number in a given space. 

 The few that can be seen appear larger than in the true types, 

 and I estimate that there are not more than thirteen or four- 

 teen in 5 mm. 



The small size and lax growth of the zoarium distinguish the 

 species from all others known to me. 



Position and locality: Keokuk group. King's Mountain, Ky. 



PTILOPORA PROUTI Hall. 



PI. LXV. fig. 3-3c. 

 Ptilopora prouti Hall, 1858. Pal. Iowa, p. 653, PI. 22, figs. 6a-6c,7. 



Zoarium a pinnate frond, attaining a height of 6 or 7 cm., 

 and a width of 5 or 6 cm. Midrib rather strong, commonly 

 about 1 mm. wide, giving off on each side about eleven or twelve 

 78 



