114 LOWER PENINSULA. 



foliated surface, and consisting of a cycle of stout vertical lamellae, 

 which incloses the central series of diaphragms. Occurs in the 

 drift of Michigan, and is found in place at the Falls of the Ohio, 

 and in the corniferous strata of Canada. 



Plate XLI. — Silicified specimens from the Falls of the Ohio. The 

 right-hand weathered specimen exhibits the centre of a polyp 

 stem intersected by diaphragms. The left-hand specimen has at 

 the conical base preserved its continuous epithecal wall ; above 

 it the surface is exfoliated and shows the coarse, blister-like cavi- 

 ties intermediate between the invaginated series of renewed cell 

 cups. 



BLOTHROPHYLLUM C^SPITOSUM, N. Sp. 



Aggregated, conico-cylindrical polyp cells of a much interrupted, 

 articulated growth, by constantly repeating constrictions and dilata- 

 tions of the cell cups. The constrictions of the stems are acute 

 angular, without interruption of the continuity of the surface walls ; 

 in other instances the continuity is interrupted, and a more or less 

 broad, expanded rim of the older cell cup projects with free edge at 

 the places of constriction. The polyparia multiply by gemmation 

 of many young cells at once from the end cups of the older stems. 

 The clustered stems become attached to each other by their acute, 

 annular edges ; the joints of the obliquely diverging stems are gen- 

 erally oblique to each other in proportion to the inclination of the 

 stems — one joint, so to say, being pushed sideways over the other in 

 this direction. The calyces are shallow, with obliquely spreading 

 side walls. Radial crests not very high, linear, and projecting most 

 on the more vertical portions of the cup walls, dilating into tent form 

 on the marginal, expanded portions of the calyces. Edges of the pli- 

 cations denticulate and surface granulose. At the margins of the 

 calyces smaller, rudimentary plications are alternately interposed 

 between the larger ones. Diaphragms forming the bottom of the 

 cups flat, with several siphonal depressions in their circumference, 

 but with no distinct septal fovea ; their centre usually smooth, 

 sometimes carinated by the ends of the lamellae. By the united 

 linear, crest-like portion of the plications a cycle of vertical lamellae 

 is formed around the central diaphragms ; the area exterior to this 

 cycle is formed by superimposed, plicate, sometimes blistered, 



