I08 LOWER PENINSULA. 



edges, and decorated by arched carinae crossing their flanks ; from 

 thirty-six to forty lamclLne in the circumference of a calyx. In- 

 terlamcllar interstices filled with delicate, transverse, vesiculose 

 plates. The central area is distinctly septate by diaphragms, 

 which are not much intersected by vertical crests ; on the circum- 

 ference of the central area, in polished transverse sections, a 

 more compact ring is visible, formed by a thickening of the longer 

 lamellee, and by the abrupt termination of the alternating shorter 

 ones within this circle, but not a trace of an actual inner wall is 

 developed. By comparing specimens from different strata and 

 different localities, a number of minor variations may be observed, 

 but I do not consider them important enough to make specific dis- 

 tinctions. This form approaches also so near to Cyathophyllum 

 rugosum of the upper Helderberg group, that a strict distinction 

 between them is almost impossible. 



Occurs abundantly in the Hamilton strata of Thunder Bay, and 

 of Little Traverse Bay; is also a common form in the Hamilton 

 strata of Iowa. 



Plate XXXVH., Fig. 4. 



CYATHOPHYLLUM CRISTATUM, N. Sp. 



Astrseiform calyces, bell-shaped, joining with polygonal, suberect 

 margins ; diameter of cells about two centimeters ; about thirty-six 

 alternately large and small stout lamellae in the circumference, with 

 crenulated edges and lateral carinations ; the larger lamellae ex- 

 tend over the bottom of the cells to the centre ; interlamellar inter- 

 stices large, filled with coarse, transverse, vesiculose plates. Central 

 area irregularly septate by vesiculose compound diaphragms. Oc- 

 curs rarely in the Hamilton strata of Little Traverse Bay ; its 

 structure is much coarser than in Cyathophyllum Davidsoni, with 

 which it is associated. 



The specimens were not sufficiently perfect for photographic 

 delineation. 



CYATHOPHYLLUM COALITUM, N. Sp. 



Astraeiform masses of very large, polygonal polyp cells measuring 

 about four centimeters in diameter, each one surrounded by its 



