226 THE DEVONIAN OF MISSOURI. 



On the celluliferous side the branches are about the same strength as on the reverse 

 side, 17 occurring in 1 cm. Fenestrules similar to those on the opposite face. Cell 

 apertures in 2 ranges, sometimes 3 just before a bifurcation, slightly oblique to the axis 

 of the branch, 16 in the space of 5 mm., separated by about half the diameter of an 

 aperture, sub-circular in outline, sometimes crowded against fenestrules and indenting 

 their borders. 



A thin section reveals the superstructure, formed by the junction of the carinae 

 and scalae. For a short distance the latter are oblique to the former, then gradually turn, 

 until at the junction they are at right angles. 



Remarks — This species resembles very closely Unitrypa lata Hall. ■ In contrast 

 the nodes common to that species have not been observed in any of the specimens studied, 

 and the scalae are somewhat thicker, and the interstices wider than the scalae. 



Horizon — Upper beds. 



Figured specimen No. 27657 Walker Museum. 



Unitrypa subcircularis sp. nov. 

 Plate 59, figures 5-7 



Description — Zoarium infundibuliform, frond rapidly expanding, size unknown. 

 Branches straight or slightly sinuous, flat, equal to or less than the width of the fenes- 

 trules, bifurcations frequent. Dissepiments strong, approximately the same width as 

 the branches, slightly rounded on the reverse side, and on the same plane with them 

 or a little depressed, expanded at their junction with the branches, 10 to 11 in the space 

 of 1 cm. Fenestrules longitudinally oval, sometimes sub-circular. 



On the celluliferous side the branches are straight to slightly sinuous, of equal 

 strength with branches on the reverse side, 12 occupy the space of 1 cm., gradually ex- 

 panding in width from .25 mm. above a bifurcation to .30 mm. below. Dissepiments 

 about the same width as the branches or a little greater. Fenestrules elongate oval, 

 length .75 to .90 mm., width about half as great, 11 occupy the space of 1 cm. Zooecial 

 apertures in ranges of 2, 12 to 13 in 5 mm., oval in outline, separated by about half the 

 diameter of an aperture. 



Carinae connected by scalae form the superstructure. Interspaces sub-circular, 

 greatest diameter .50 mm., scalae thick, carinated, 30 in the space of 1 cm., expanded 

 considerably where they join the carinae. 



Remarks — This species resembles Unitrypa tegulata Hall, but the apertures are 

 more widely disposed than in that species. 



Horizon — Upper beds. 



Hololype No. 27655 Walker Museum. 



Genus Polypora McCoy 



Polypora cf. hexagonalis Hall 

 Plate 60, figures 1, 2 



1883. Fenestella hexagonalis Hall, Trans. Albany Inst. 10, p. 169, (abstract 1881, 



p. 27). 

 1887. Fenestella {Polypora) hexagonalis Hall and Simpson, Pal. N. Y., vol. 6, p. 164, 



pi. 33, figs. 14-20. 

 Description — Zoarium apparently infundibuliform, size unknown. Surface essen- 

 tially smooth on the reverse side. Branches of medium strength, sinuous, rounded, 

 gradually enlarging from .40 mm. above a bifurcation to .90 before. Interstices wider 

 than branches. Dissepiments rounded, about same strength as branches, and on the 

 same plane, 3 present in the space of 5 mm. Fenestrules oval, outer rim hexagonal, 

 length to width in proportion of 3 to 2. 



