BRYOZOA. 505 



T.ENIOPORA OCCIDENTALS Ulrich. 

 PI. XT.TT, fig. 3 3C. 



This species differs from penniformis Xich., a transverse sec- 

 tion of which is figured on PI. XLII, fig. 3d for comparison, in 

 the following- points. The zoariuni is not so wide, but has a 

 more solid appearance; the median keel is subangular and not 

 nearly so thin nor so prominent, the non-poriferous margin is 

 narrower. The apertures of T. penniformis are strongly ele- 

 vated and arranged in slightly oblique transverse rows (sug- 

 gesting the name). In this species the arrangement of the 

 apertures in longitudinal series between low rounded ridges is 

 more striking than that in transverse rows, while the peristonie 

 is so little developed that it is scarcely perceptible. Internally 

 T. penniformis has the interstitial vesicles open, while in the 

 western form they are filled by solid tissue. T. exigua Nich., 

 the only other described species of the genus is a smaller form. 



The width of the branches in T. Occident alis, which bifurcate 

 at intervals of eight mm. or more, is between 2.5 and 3 mm. 

 The zocecia apertures are subcircular. in four longitudinal rows 

 on each side of the median keel, with from seven to nine in 

 three mm. measuring longitudinally. Their diameter increases 

 from 0.09 mm. in the central rows to 0.13 mm. in the marginal 

 series, the increase being proportional in each succeeding row. 

 A shallow depression is often observed in front of the aper- 

 tures. 



Position and locality: Hamilton group; Buffalo, Iowa. 



PRISMOPORA Hall, 1881. 



(Bry. Up. Held. p. 17.) 

 (For generic diagnosis see page 386.) 



PRISMOPORA TRIFOLIA Rominger. 



PI. LXXVH, fig, 4, 4a. 

 Fif("Ufora irifolia Rominger, 1866. Proc. Acad. Nat. Sci. Phila. p. 122. 



Zoariuin consisting- of triangular branching stems, growing 

 from a large spreading base attached to foreign objects. The 

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