70 THE DEVONIAN OF MISSOURI. 



meters. Fenestrules varying slightly in size, but averaging 4 to 5 in 10 millimeters, 

 measured longitudinally. Branches subcarinate and following zigzag courses on the 

 non-celluliferous face. Zooecial openings about 7 to 2 millimeters, 2 to 4 rows between 

 the fenestrules. 



This species resembles Fenestella perundata Hall, but the fenestrules are much 

 smaller than in that form and are more regularly arranged. 



Occurrence — Mineola of Montgomery County. 



Genus Hemitrypa Phillips 



Hemitrypa mineolaensis n. sp. 



Plate 9, figures 10, 11,12; plate 10, figure 5. 



Zoarium known from numerous fragments and from one fairly complete specimen. 

 On the reverse side many of the branches are nearly straight while others are slightly 

 zigzag, 9 to 11 in 5 millimeters, rounded, and with considerable variation in width. 

 Dissepiments short, slenderer than the branches, ranging from opposite to alternate in 

 adjoining rows, generally rising above the branches and forming interrupted zigzag 

 ridges. Fenestrules oval to nearly circular, about .4 mm. by .2 mm., with about 14 in 1 

 centimeter. 



On the obverse side the branches appear narrower than on the reverse and are not 

 so broadly rounded at the top. Zooecial pores in two parallel ranges, opening obliquely 

 toward the fenestrules, 3 or 4 to each fenestrule, 23 in 5 millimeters. 



The network on the obverse side is very delicate. The principal bars are easily 

 distinguishable from the secondary on account of their greater width and height; the 

 lateral bars are like the secondary, and there are about 23 in 5 millimeters. 



This species differs from Hemitrypa tenera Ulrich, in the circular shape of the 

 openings in the network on the obverse side, the larger size of the principal bars on this 

 side, in the larger size of the branches of the zoarium, comparatively slenderer dissepi- 

 ments, and higher dissepiments uniting to form ridges. 



Remarks — This is the most abundant fossil in the Mineola limestone. 



Occurrence — Mineola limestone of Montgomery and Warren Counties. 



Family Rhabdomesontidae 

 Genus Rhombopora Meek 



Rhombopora missouriensis n. sp. 

 Plate 9, figure 6; plate 10, figure 2. 



Description — Zoarium branching dichotomously at intervals of 5 to 10 mm. usu- 

 ally spreading in one plane but sometimes in various directions. Branches from 0.5 

 to 3 mm. in diameter. Zooecia proceeding out from the axis of the branch at an angle 

 of about 80°. Zooecial apertures small, oval, 0.2 mm. long, arranged in longitudinal 

 and diagonal intersecting series. 7 in 2 mm. in the first, and 9 to 10 in 2 mm. in the 

 second. In some specimens the rows are very irregular. Interspace generally ridge- 

 shaped, the summits rather sharp, enclosing oval depressions which are steep sided at 

 the lower side and gently sl'oping from the upper. 



Rhombopora subannulata Ulrich, from the Devonian of Iowa, has a similar ex- 

 ternal appearance but has tubercles at each angle of intersection of the surface ridges 

 and the zooecia branch out at a much smaller angle. 



Occurrence — Abundant near the top of the Snyder Creek, in the Stromatoporoid 

 zone in Callaway County. 



