BRYOZOA. 499 



favorably with species from the St. Louis limestone than with 

 the Devonian form next described. 



Position and locality: Niagara group; Will Co., 111., near 

 Wilmington. 



DlCHOTRYPA FOLIATA, UMch. 

 PI. XLII, Fig. 2-2g. 



Zoarium palmate, or an explanate undulating frond. Entire 

 dimensions unknown but attaining a height and width of six or 

 eight cm.; thickness two mm. or less. Surface even, but marked 

 with slightly depressed, circular or elongate, solid maculae, 

 arranged in more or less regular series, three or four mm. apart 

 measuring lengthwise. Apertures arranged in linear series between 

 longitudinal ridges. These ridges are most prominent in worn 

 specimens; when the surface is well preserved they scarcely show 

 and in this case the arrangement of the cells in diagonally in- 

 tersecting series, due to their alternation in adjoining rows, is 

 most conspicuous. Apertures circular, 0.12 to 0.15 mm. in 

 diameter, their own diameter or somewhat more apart, about 

 eight in three mm., measuring either longitudinally or diago- 

 nally. Peristome a little more elevated on one side than on the 

 other. Primitive zooecia prostrate, of semi-cordate form, with 

 the vestibule tubular and almost rectangular to the surface. 

 Walls of vestibular portion of zooecia ring-like, traversed at the 

 posterior side by a small vertical pore. Lunarium very faint' 

 Interspaces filled in the deeper parts of the zoarium with small 

 vesiculse; as the surface is approached these give way to solid 

 tissue. Superior hemiseptum, when preserved, strong and pro- 

 jecting well into the zooecial cavity. 



This beautiful bryozoan cannot be confounded with any other 

 form known to me from the Hamilton group. The longitudinal 

 arrangement of the zooecia apertures distinguishes it from other 

 species of the genus. 



Position and locality: Hamilton group, Buffalo, Iowa. 



