BRYOZOA. 321 



Spatiopora iowensis.l * 



never exceeds 1 mm. Diaphragms are wanting in most of the tubes, but here and 

 there the sections pass through one or several adjoining tubes having one diaphragm 

 about midway up and sometimes another at the mouth. 



This is an interesting and easily recognized species. Of associated parasitic 

 forms only two need be compared; one, Stromatotrypa ovalis of this work, has oval 

 and much larger zocecia; the other is a rare and as yet undetermined form with 

 circular and smaller zooecia, numerous mesopores, and more uneven zoarium. S. 

 labeculosa differs from both in the greater size and distinctness of its maculae, and in 

 the slight" obliquity of its zocecial apertures. The maculae will distinguish the species 

 at once from all the other species of the genus. 



Formation and locality. In the middle third of the Trenton shales at Minneapolis and St. Paul. 

 Mus. Reg. No. 5026. 



SPATIOPORA IOWENSIS, n. sp. 



(Not figured.) 



Zoarium spread as an exceedingly thin crust over the cones of Orthoceras sociale 

 Hall. Monticules wanting, but unusually distinct clusters of large cells are dis- 

 tributed over the surface at intervals of about 5 mm., measuring from center to 

 center. Zocecia larger than in other species of the genus, their walls thin, the 

 apertures nearly or quite direct, angular, often of hexagonal or rhombic shapes, with 

 three of those in the clusters in 2 mm. and an average of nine of those in the spaces 

 between the clusters in 3 mm. Mesopores wanting except in the clusters mentioned 

 where a few may be wedged in among the large cells. Many of the angles of junc- 

 tion between the apertures are raised into sometimes small, at other times large, 

 acanthopore-like prominences. 



In the dark shales at Graf, Iowa, this bryozoan is preserved as a thin gladiolus 

 leaf-like film, the Orthoceras grown upon being compressed to such a degree that its 

 original presence may not be suspected. 



This species is in every respect a true Spatiopora. The affinities are nearer 

 S. maculosa Ulrich, of the Cincinnati rocks, than to any of the others, and it is with 

 that species that I first thought to place it. On comparison however S. iowensis 

 proved to have larger zocecia, with eight to ten where the Ohio species has eleven or 

 twelve. 



Formation and locality. Maquoketa shales of the Hudson River group at Graf, Iowa. 



Mus. Reg. Nos. 7586, 7587. 



-31 



