BRYOZOA. 429 



appreciably as they near the surface. Zooecia eight or nine in 

 the space of two mm., with circular or oval apertures 0.15 to 

 0.2 mm. in diameter. Zooecia separated by angular or subcir- 

 cular mesopores arranged in a single or double series, some- 

 times forming small clusters. Mesopores from one-half to three- 

 fourths as large as the zooecia. Diaphragms fairly abundant 

 throughout the zooecial tubes, very numerous and closely set in 

 the mesopores. Sections present obscure evidences of the dia- 

 phragms of the mesopores having a central perforation. Acan- 

 thopores numerous and of large size. 



The figure of the tangential section (PI. LXXY. fig. 8b) does 

 not represent the structure as well as it might. Some of the 

 acanthopores are made too prominent and others overlooked 

 entirely. This is due to the peculiar fossilization by which the 

 internal characters are much obscured. The globose form in 

 connection with the strong tabulation easily distinguish this 

 species from the other species of the genus. 



Position and locality: Kinderhood group. Marshalltown. la. 



LEIOCLEMA GRAciLLmrM Ulrich. 



PI. LXXV, fig. 6, 6b. 



Zoarium ramose, branching regularly; branches from one to 

 one and a half mm. in diameter. Surface even. Apertures of 

 zooecia elliptical, about 0.15 mm. in their longer diameter, and 

 0.1 mm. in their shorter diameter, eight or nine in two mm.; 

 surrounded by a large number of very small mesopores. Acan- 

 thopores small, numerous. 



This species is closely allied to L. punctatum, but is distin- 

 guished from it by its smaller cells, and smaller branches, which 

 are also more constant in size. It seems to have an extended 

 vertical range. The typical form is from the Keokuk group. 

 Specimens which cannot be distinguished from the typical forms 

 are found in the Kinderhook. Burlington and Warsaw groups. 



Position and locality: Occurs at most localities of the Keokuk 

 group: in the Kinderhook group at Marshalltowu. la: in the 

 Burlington group at Burlington, Iowa, and in the Warsaw beds, 

 at Warsaw. 111. 



