BKYOZOA. 609 



tion very wide, usually about 90. Zooecia small, in from five 

 to nine ranges. About two-thirds the circumference of the 

 branches is taken up by their apertures, the remaining third 

 being non-celluliferous, and smooth or very finely striated. On 

 the obverse face of the widest examples the zocecia apertures 

 are arranged in oblique curved series very much as in T. divan- 

 cans (PI. 62, fig. 6a). The series, however, are much closer 

 together, there being ten in 3 mm., the apertures smaller (about 

 0.07 mm. in diameter,) less pronounced, and surrounded by a 

 thin peristome. The central rows especially are also arranged, 

 in longitudinal series between distinct elevated lines, causing the 

 formation of a deeply concave oblong space behind each aper- 

 ture. As intimated, this concave space becomes gradually less 

 distinct on the sides of a branch, and disappears entirely before 

 reaching the irregular rows that margin the non-celluliferous 

 space. In narrow or young examples the arrangement is as 

 shown in fig. 8a. 



This species is peculiar in the wide angle at which the branches 

 bifurcate, the depressed space behind the zocecia apertures, the 

 small size of the zooecia. the subcylindrical form of the branches, 

 and the narrow non-poriferous space. These features distinguish 

 it from all the species of the genus known to me. 



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



THAMNISCUS FUBCILLATUS Ulrich. 



PI. LXH, fig. 9,9b. 



Zoarium small, consisting of slender, dichotomously divided 

 branches, increasing very gradually from 0.5 to 0.6 or 0.7 mm., 

 between the bifurcations. Bifurcations terminal, widely sepa- 

 rated, rarely less than 7 mm. apart, but varying between the 

 extremes of 4 and 9 mm. Angle of bifurcation between 60 and 

 90. Zooecia usually in four ranges; in three or four just after, 

 and four or five just before bifurcations. Apertures small, sub- 

 circular, 0.08 mm. in diameter, about seventeen in 5 mm., with 

 a peristome, alternating in adjoining rows, the rows separated 

 by more or less continuous elevated lines, which often carry 

 small nodes. The nodes, however, are never conspicuous. Both 

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