Bryozoa of the Hamilton Group. 71 



a similar ridge ; though not invariably, as the specimens, so far as 

 observed, never occur with the poriferous face free, and the carina being 

 extremely thin, so that in separating from the rock it might possibly 

 be that the carinse of the dissepiments, if any exist, are broken. The 

 non-poriferous face, on different portions of the frond, presents a 

 variety of appearances ; on some portions apparently the branches 

 have a continuous carina very thin and but slightly elevated and the 

 dissepiments with a semi-circular carina, not connecting with the car- 

 ina of the branch ; on other portions the fenestrates are surrounded 

 by thin elevations, the space between being somewhat flattened and in 

 the wider portions having slightly elevated irregular lines and in the 

 narrower portions pustulose. 



This species can be distinguished from F. exornata by its coarser 

 appearance as well as by the different ornamentation of the non-porif- 

 erous face of the branches. 



Formation and locality. Hamilton group ; Moscow, Livingston 

 county, N". Y. 



c( Fenestella subtortilis. n. sp. 



Probably infundibuliform m shape, but occurring only in fragments; 

 largest fragment observed three centimetres long and two and one-half 

 in diameter. 



Branches comparatively slender, of nearly the same width through- 

 out their entire length; bifurcations distant; width of branches from 

 .25 to a little more than .-33 mm. ; space between equal to or a little 

 more than the width of the branches ; nine branches in the space of 

 five millimetres; where the dissepiments on opposite sides of the 

 branches alternate, which is generally the case, the branch is regularly 

 flexuous ; on non-poriferous side the branches are moderately convex, 

 and w r ith a thin, slightly elevated carina running along the middle 

 which is frequently obliterated by weathering; the carina is finely 

 nodose, the rest of the branch is also nodose or granulose ; branches 

 wider on poriferous side, giving the appearance of being more densely 

 arranged than on the non-poriferous side. 



Dissepiments strong, as wide or wider than the branches, six in the 

 space of five millimetres; on non-poriferous side, on a plane with 

 or elevated slightly above the branches, rounded, carinated ; carina 

 thin, slightly elevated and connecting with the carinas of the branches; 

 on poriferous side depressed, narrower than on the non-poriferous side. 



Owing to the branches being widest on the poriferous side, the 

 appearance of the fenestrules on the poriferous face varies from that 

 of the non-poriferous side; on which side they are' broadly oval or 

 circular; length about .5 mm. ; width from three-fourths to equal the 

 length ; on poriferous side they appear much narrower, the branches 

 sometimes being nearly contiguous. 



Cells in two ranges, opening directly upward ; apertures minute, 

 circular, about .20 or .16 mm. in diameter ; distance apart equal to or 

 less than the diameter of an aperture, eighteen in the space of five 

 millimetres ; margins thin, elevated ; space between ranges of apertures 

 carinated; carina at first very thin, sinuous, thickening immediately 



