242 



Cincinnati Society of Natural History, 



141, Plate V., figs. 3-3/, 1881). His figures of that species fail to 

 represent two of the most important characters, nor are they mentioned 

 in his description, viz: the connecting foramina, and cystoid dia- 

 phragms. I feel confident that his sections were prepared from a 

 portion of a frond not fully matured, since his figures and description 

 of the internal characters of the species, apply in all respects to sec- 

 tions prepared by me from examples in that condition. In a tan- 

 gential section of a full} r matured specimen, cutting the tubes just 

 below the surface, the walls of same have a thickness about equal to 

 those of H. curvata, as represented by fig. 7c/, Plate X., and the con- 

 necting foramina (clearly shown in one of my sections), are precisely 

 like those piercing the walls of the tubes in H. obliqua (Plate X, 

 fig. 66). The cystoid diaphragms are large, and developed in only a 

 minority of the tube^, and in this character II. dawsoni differs from 

 all the other species of the genus. This species is further character- 

 ized by its frondescent growth, and remarkably prominent and closety 

 arranged monticules. 



Homotrtpa curvata, n. sp. (Plate X., figs. 1-ld.) 



Zoarium ramose, consisting of compressed, often greatly flattened 

 branches. An average specimen has a height of over two inches, a 

 width of about seven tenths of an inch, and a thickness of two tenths 

 of an inch. The most conspicuous feature of the surface is found in 

 the small, stellate maculae, which, under a low magnifying power, ap- 

 pear to be solid, but, as is shown by a higher power, are composed of 

 very shallow, and angular, small cells. These maculae are on a level 

 with the general surface, and occur at intervals of about .11 of an inch, 

 measuring from center to center. The ordinary cells are usually 

 rounded, though sometimes slightly angular, have moderately thick 

 walls, with a diameter varying from y^-oth to xio"^ 1 °f au i nc h. The 

 cells immediately surrounding the stellate maculae are larger, and may 

 attain a diameter of -g^th of an inch. When the specimen examined is 

 in a good state of preservation, the surface spines (spiniform tubuli) 

 ma}' be detected. The}* never constitute a conspicuous feature of the 

 surface. 



Tangential sections (Plate X., fig. 7c?) show that the tubes in the outer 

 or " mature" portion of the zoarium have thickened walls, more or less 

 rounded visceral cavities, and that the}' are apparently completer- 

 amalgamated with one another. The walls, between the narrow lucid 

 ring which surrounds each of the tubes, has a peculiar granular 



