BRYOZOA. 449 



Position aiid locality: St. Louis group, Fella, Iowa. A simi- 

 lar species, having somewhat smaller cells, occurs in the Chester 

 limestone. 



AMSOTRYPA RAMULOSA Ulrich. 



PL LXXTI, flg. 7, 7o. 



In its minute structure this species closely resembles A. fistu- 

 losa, from which it may be distinguished by its consisting of 

 small solid branches, from three to six mm. in thickness. The 

 cell apertures are about of the same size and shape, though, 

 perhaps always, separated by slightly thicker walls, and there 

 are clusters of large sized apertures. The minute structure of 

 the walls and the arrangement of the perforated diaphragms 

 in the mature region are not materially different. Vertical sec- 

 tions will of course be distinguished immediately by the solid 

 axis of the present species. The zooecial tubes in the axial re- 

 gion have very thin walls, and so far as observed are not 

 crossed by diaphragms. 



Position and locality: St. Louis group. Pella, Iowa. 



AMSOTRYPA SOLIDA Ulrich. 



PL LXXH, flg. 9-9e. 



Zoarium consisting of solid cylindrical stems, branching di- 

 chotomously and otherwise. The examples from Sloan's Valley, 

 Ky.. average three mm. in diameter, those from Chester, 111., 

 nearly five mm. Surface with clusters of cells a little larger 

 than the average, which are only conspicuous when they are 

 slightly elevated. Zooecia polygonal, usually hexagonal, vary- 

 ing in width from 0.28 to 0.45 mm. in the clusters, nine or ten 

 of the average size in three mm. Apertures oval or subcircu- 

 lar, rarely angular. Zooecial tubes curving gradually from the 

 axial region to the surface where they are direct. Walls thin 

 in the axial, very much thickened in the narrow cortical region, 

 where they may present one or two faint constrictions. Adjoin- 

 ing- zcKHcia separated by a well marked divisional line. Inter- 

 spaces thick and ridge like. Three or more perforated dia- 

 phragms intersect the tubes in the mature region. Dark spots 

 56 



