420 PALEONTOLOGY OF ILLINOIS. 



to reach the surface. Walls thin in the axial region, thickened 

 but little towards the surface. Zooecia often in contact, with 

 apertures sometimes oval, usually pyriform, narrowing above, 

 surrounded by a narrow peristome, obsolete or less distinct at 

 the upper end; about six or seven in the space of one mm. 

 measuring longitudinally, and eight to ten measuring trans- 

 versely, arranged in irregular, obliquely ascending lines. Inter- 

 stitial spaces irregular, more or less depressed, apparently solid 

 at the surface, but in thin sections seen to be occupied by 

 elongated mesopores. Acanthopores moderately abundant, 

 small, sometimes conspicuous. Diaphragms two or three in the 

 mesopores, rarely present in the zocecial tubes. 



This species is associated with a number of other small forms, 

 from all of which it is readily separated by its very much 

 smaller cells, and characteristic pear-shaped openings. This is 

 probably the smallest species of the genus. Its small size and 

 pyriform apertures at once distinguish it from its nearest con- 

 geners T. debilis and T. primigenm Ulr. 



Since the above was written a large series of specimens of 

 this species have been collected. These show that the base of 

 the branches was pointed and that the zoaiium was jointed at 

 irregular intervals. It is, therefore, probable that the species 

 belongs to another genus. 



Position and locality: Cincinnati group, at Savannah, 111., 

 where it is very abundant at an horizon about 150 feet above 

 the river. 



TREMATOPORA CALLOPOROIDES Ulrich. 



PL XXXIV, flg. 1-ld. 



Zoarium irregularly ramose, branches from four to seven mm. 

 in diameter. Surface marked by faint monticules whose centers, 

 occupied by sub-stellate groups of mesopores with closed aper- 

 tures, present an apparently solid aspect. Distance between 

 centers of monticules two or three mm. Zocecial tubes run 

 irregularly in the a.xial region, curve gradually, and at the sur- 

 face are almost direct. Walls thin in the axial region and but 

 little thickened in the cortical region. Zooecia seven or eight in 

 the space of two mm., with sub-angular or sub-circular aper- 



