﻿48 



Cincinnati Society of Natural History. 



that this deposit was perforated, but judging from the evidence at 

 hand, and especially that afforded by one of the vertical sections, and 

 the very minute pits shown in many specimens, I should say that such 

 was actually the case, and I do not doubt that I will yet find a sec- 

 tion that will show it in an unquestionable manner. The zooecia are 

 elliptical, and at a deeper level are separated generally by one or two 

 series of small angular interstitial vesicles; one section, prepared from 

 an old example, shows occasionally three rows. The zooecial walls , 

 are very thin in front, becoming gradually much thicker on the pos- 

 terior side. In old specimens the anterior portion of the wall is also 

 appreciably thickened just below the surface. 



In longitudinal sections (PI. III., fig. 46) the zoarium is centrally 

 divided by a thin but double lamina, to which the small end of the 

 tubes is attached, and from which they proceed with a gentle curve 

 obliquely outward to the surface. The upper or anterior wall is wavy 

 and thin throughout the entire length, excepting in old examples, when 

 at the aperture it is slightly thickened by a secondary deposit on the 

 inside. The lower or posterior wall is always much less sinuous, and 

 in the outer portion of the zoarium appreciably thickened. The tube 

 cavit}^ is crossed by straight diaphragms, a tube diameter or a little 

 less distant from each other. Interstitial vesicles at first large, grad- 

 ually becoming smaller and more numerous toward the surface, near 

 which the space occupied by them is filled by a dense deposit of 

 sclerenchyma, varying in thickness with age. In one section there are 

 very good indications that the deposit was perforated by minute ver- 

 tical canals. 



In transverse sections the central lamina, which separates the 

 zoarium into two equal portions, does not extend through to the edges 

 of the branch. The duplex character of the lamina is, in some places, 

 distinctly shown, and between the two plates there is a series of capillary , 

 tubes, which in this kind of section ar ; divided transversely, and con- 

 sequently have a longitudinal direction. On each side of the median 

 line there is a series of small quadrangular cells; between these and 

 the dense peripheral region, extending completel}* around the branch, 

 the interstitial vesicles are at first large, then gradually decrease in 

 depth outwardly, at the same time also increasing in numbers. 



In the characters of the zooecia and form of the zoarium this 

 species differs considerabty from the tj-pical forms of the genus, and 

 I am not certain that an examination of other similar species will not 



