136 LOWER PENINSULA. 



linear, crcst-shapcd in the circumference of the inner pit, and ex- 

 tending:^ over the surface of the diaphragms, gradually vanishing 

 near the centre. In their divergence across the expanded margi- 

 nal parts, the plications lose the crest form and dilate into low, 

 rounded, gradually widening rugae with intermediate linear fur- 

 rows. The surface of the expanded parts of the calyces is raised 

 into blisters, locally densely crowded, and obscuring the radial folds ; 

 in other parts singly dispersed. The central diaphragms are sim- 

 ple and not blistered. In vertical sections the polyparia fully re- 

 semble a Cystiphyllum, being composed of layers of coarse, un- 

 equal, interlaced vesicles. The calyces attain in some specimens a 

 diameter of from three to four inches. Found in the Niagara 

 group, at Point Detour, and on Drummond's Island. 



Plate XLIX., right-hand figure, upper row. — In the Niagara 

 group of Masonville, Iowa, another species of more minutely vesic- 

 ulose structure occurs, which I have named Vesicidaria minor, and 

 represented, for sake of comparison, on the same plate with the 

 other. The plications are very delicate, ornamented with spinulose 

 projections ; the cell pits, scarcely depressed, are only perceptible 

 by the convergence of the plications toward certain centres. Un- 

 der side of the expansions covered by a concentrically wrinkled 

 epitheca, with radiciform excrescences for attachment to foreign 

 bodies. Associated with these compound specimens are single 

 polyp cells of the same vesiculose structure, which connect the 

 compound forms so closely with Cystiphyllum, that it would have 

 been more appropriate, perhaps, instead of establishing a new sub- 

 genus Vesicidaria, to change Milne-Edwards' original definition of 

 Cystiphyllum so as to include the compound forms with con- 

 fluent cell cups. 



VESICULARIA VARIOLOSA, N. Sp. 



Confluent calyces forming mamiform monticules, truncate by 

 abrupt but shallow cell pits, the bottoms of which are formed by 

 flat diaphragms with marginal depressions indicating the principal 

 septal fascicles. Distance from centre to centre of the monticulose 

 calyces about two centimeters ; diameter of terminal cell pits about 

 five millimeters. Calyces surrounded by about thirty plications, 



