576 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



Externally, however, the two species are readily separated by their 

 different methods of growth, the ramose zoarium of IL ohUqua, with 

 its cylindrical or slightly compressed, more or less tul^erculated, 

 branches being quite characteristic. In the Fairmount beds of the 

 Cincinnati area a form of the species with strongly tuberculated, cylin- 

 drical branches seldom over 5 or 6 mm. in diameter, occurs very 

 abundantly. The succeeding Bellevue beds also hold the species in 

 abundance, but here the zoarium is more robust and the branches are 

 often subc3'lindrical and nearly smooth. Specimens 6 cm. or more in 

 length without dividing and 15 mm. in diameter are often found. 

 The prevailing form of zoarium in the Corryville beds is a rather 

 broad, somewhat compressed, tuberculated branch, and specimens of 

 this kind probably led Nicholson to identify II. dawsoni at Cincinnati. 

 The internal structure of these various forms of the species is essen- 

 tially the same. About 10 zooecia in 2 mm. 



Occurrence. — An abundant species of the above-mentioned divisions 

 of the Lorraine at many localities in the Cincinnati area. The t3^pical 

 form occurs in the Bellevue beds. 



Cat. Nos. l:l736-tlTiO, U.S.N.M. 



HOMOTRYPA CINCINNATIENSIS, new species. 

 Plate XXI, figs. 4-10. 



Zoarium small, generally less than 3 cm. in height, ramose, dividing 

 rather regularly at short intervals; branches subcylindrical but with a 

 tendency to become frondescent, 2 to -t mm. thick and 3 to 9 nun. 

 wide. Surface commonly smooth, the clusters of usually larger cells 

 rarely forming low monticules. Zooecial apertures angular, direct, 

 about nine in 2 mm. A moderate number of mesopores present both 

 in the clusters and elsewhere. Acanthopores small, varying in num- 

 ber, sometimes as many as eight or ten surrounding a zooecium. Dia- 

 phragms and cystiphragras rather numerous and developed in the 

 peripheral region only. 



The shape of the zoarium, the small cells and smooth surface char- 

 acterize this species. The points of difference from IL duuiosa^ prob- 

 ably its nearest relative, are indicated under the description of that 

 form. 



Occurrence. — Common in the Fairmount beds of the Lorraine forma- 

 tion at Cincinnati, Ohio, and vicinity. Apparently the same form 

 occurs at Maysville and McKinneys, Kentucky, at the same horizon. 



Cat. Nos. 41742-41746, U.S.N.M. 



HOMOTRYPA DUMOSA, new species. 



I'late XX, fig. 1 ; Plate XXI, figs. 1-3. 



Zoarium consisting usually of small, inosculating, palmate branches, 

 an average entire colony being 5 cm. high and from 3 to 5 cm. in width; 



