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Cincinnati Society of Natural History. 



tudinal and transverse sections of Gheilotrypa ostiolata on Plate III., 

 figs. 7 and la show the axial tube, and other characteristic features 

 of the genus. Tangential sections show that the zooecia are obovate, 

 being rounded more acutely below, and separated from each other b} T 

 a single series of comparatively large interstitial vesicles, which, at 

 somewhat irregular intervals, form small, inconspicuous groups or 

 maculae. 



The characters above ascribed to the genus are, I think, sufficiently 

 different from those marking the other genera of this family, to warrant 

 the new generic division. 



Gheilotrypa hispida, n. sp. (PI. III., figs. 6, 6a, 66, 6c, 6d.) 



Zoarium ramose, branches cylindrical, small, from 0.04 to 0.08 of 

 an inch in diameter, dividing irregularly at variable intervals. Zooecia 

 arranged in quite regular obliquely intersecting series, in which eight 

 or nine occur in the space of 0.1 inch; small maculae, around which 

 the cells are a little larger than usual, are generally present; cell aper- 

 tures oblique, sub-elliptical, or circular, l-120th of an inch in the long 

 or vertical diameter, with the margin strongly elevated and arching on 

 the lower or posterior side; lip graduall}- diminishing on the sides, 

 until it becomes obsolete at the anterior end of the aperture. Inter- 

 stitial spaces and maculae smooth and concave, wider than the zooecial 

 apertures, which in some specimens are closed by opercula. 



Tangential sections (PI. III., fig. 6a) show that just below the 

 surface of matured examples the interstitial spaces are filled by a 

 dense deposit of sclerenchyma, in which the elliptical zooecia are dis- 

 tinctly defined; their walls are comparatively thick below, and linear 

 on the upper side. At a lower level the interstitial vesicles are shown. 

 These are small and form between each pair of zooecia two, often three 

 rows. 



Longitudinal sections (PI. III., fig. 66), passing through the cente 1 ' 

 of a branch, show the irregular axial tube, to which the small or inner 

 ends of the zooecia are attached. Man3 T of the zooecia have the aper- 

 tures closed, and farther down are crossed by a few exceedingly thin 

 diaphragms. The interstitial spaces enlarge rapidly and are occupied 

 by a closely woven vesicular tissue. The vesicles may remain open 

 to the surface, where a dense interstitial deposit closes them; or, as 

 was the case in the section figured, this deposit may extend to a 

 deeper level. 



Transverse sections (PL III., figs. 6c and 6a*) clearly show the vari- 



