BRYOZOA. 557 



Carina strongly elevated, flexuous, but little thickened at the 

 summit, frail, easily broken or worn away. Zooecia in two 

 ranges separated by a keel. Apertures circular, 0.09 mm. in 

 diameter, their diameter or more apart, twenty-two in 5 mm. 

 On the sides of the branches, but always opposite a dissepi- 

 ment, are a number of large, irregularly distributed, shallow, 

 thin rimmed sub-circular cells, about 0.3 in diameter, extending 

 from the keel nearly across the dissepiment. Their number is 

 variable but the average is about as shown in the figure. Simi- 

 lar structures are known to be possessed by several species of 

 Fenestella, and unless they represent ooecia, their nature is not 

 understood. As usual in species of this genus, near the base the 

 carinse are covered by a thin calcareous membrane, and the 

 space under this and between the branches, is filled with loosely 

 woven vesicular tissue. On the reverse the fenestrules are oval 

 or sub-rhomboidal and arranged in regular diagonally inter- 

 secting series, eleven or twelve in 1 cm. The branches are thin- 

 ner than the width of the fenestrule, carinate when w T ell pre- 

 served, zigzag, and united by inosculation so as to form regular 

 rhombs. The point of junction or intersection is more or less 

 prominent. 



This fine species is distinguished by the flexuous branches, 

 and the large cells (? ooecia). S. rhomboideum Prout, has fif- 

 teen fenestrules where this has only twelve. They are besides 

 not so regularly rhombic. 

 'Position and locality: Hamilton group; Buffalo, Iowa. 



FENESTRAPORA Hall, 1887, (1885?) 



(Pal. N, Y. Vol. XVI, p. XXH.) 

 (For generic diagnosis see page 395.) 



At first I was not inclined to admit this genus, but the sub- 

 sequent finding of the dimorphic pores in three distinct species 

 has convinced me of its claim to recognition. As regards the 

 nature of these pores, I can only suggest a comparison with 

 the "avicularian" cells of the Chilostomata. 



