BRYOZOA. 417 



the exception of C. perelegans none of the species more recently- 

 referred to Callopora by Prof. Hall seem to have the essential 

 characters of the genus. 



Thin sections of Callopora exhibit a remarkable uniformity 

 of structure, and it is sometimes very difficult to discriminate 

 between those of closely allied forms. TJiis uniformity is more 

 especially apparent in transverse and vertical sections, but as 

 these are highly diagnostic of the genus, they are necessary to 

 confirm the generic reference. Most of the species form large 

 bushy masses, and the Cincinnati group deposits often furnish 

 some very showy cabinet specimens. 



CALLOPORA SUBXODOSA Ulrich. 



PI. XXXIII, fig. 5-5c. 



Zoarium ramose: stems subcylindrical, from six to twelve 

 mm., or even more in diameter. Surface sometimes nearly 

 smooth, usually tubercled. Tubercles rounded, never conical, 

 more or less elevated, composed of apertures rather larger than 

 the average, and numerous mesopores. Zooecial walls com- 

 paratively thin throughout. Zooecia approaching the surface 

 in a gentle curve, about seven in two mm.; with circular aper- 

 tures, ranging from 0.18 to 0.27 mm. in diameter; surrounded 

 by a variable number of angular or subcircular mesopores. 

 The zooecial tubes expand very gradually from the point of 

 their origin until they attain their normal size. In the first 

 part of their course, they have several diaphragms about their 

 own diameter apart: after that, diaphragms become rare and 

 may be entirely absent in the rest of the zooecial tube. The 

 mesopores are tabulated very closely throughout; about three 

 diaphragms in a space equalling their own diameter. 



This species differs from the common C. ramosa d'Orbigny 

 in the less prominent monticules, which are rounded instead of 

 conical. The tabulation of the tubes in the two species is also 

 very different. Though very distinct from (_'. elegantula Hall, 

 the type of the genus, it is more nearly related to that form 

 than is any other known species of the genus. 



Position and locality: Upper beds of the Cincinnati group, 

 Blanchester. <).. and numerous other localities. A variety oc- 

 -iirs at Wilmington and Savanna, 111. 

 52 



