19'*^ Cincinnati Society of Natural History. 



M. impiicaia (Ulrich) Nicholson. Corallum dendroid, stems 

 flattened, three lines wide and one and a half to two lines 

 thick, branching at intervals ; calices 7^ to ^V inch in diameter, 

 irregularly oval, often indented on one or both sides, thick- 

 walled with numerous blunt spines ; between the ordinary 

 calices are occasional smaller apertures ; average corallites 

 thin-walled in the central region, but becoming greatly thick- 

 ened as they approach the surface, the original lines of 

 demarkation between the tubes never being entirely obscured ; 

 small corallites developed in variable numbers ; numerous 

 circular, hollow tubes interspersed in the thickness of the 

 walls and at the angles of junction of the cells ; remote, com- 

 plete and approximately horizontal tabuk^, somewhat more 

 numerous in the small than in the large corallites. 



26. — M. QUADRAT.\ Rominger, 1866. 



Corallum dendroid, occasionally sub-massive, branches 

 cylindrical, varying from two to five lines in diameter, often 

 ending in bulbous extremities ; surface smooth or nearly so ; 

 corallites thin-walled below, slightly thickened toward the 

 mouths, all similar; calices in places obliquely rhomboidal, 

 sometimes polygonal, arranged in regular diagonal rows, the 

 direction changing at short intervals ; lips very thin ; no inter- 

 stitial tubes; tabulse nearly wanting or very sparingly devel- 

 oped in the axial region, but a moderate number present in 

 the outer portions of the corallites ; tabulation in all the tubes 

 alike horizontal and complete. {C/ialetes qiiadratus Rom., 

 Proc. Phila. Acad. Nat. Sci.. 1866, p. 115.) {Chcetetes rhom- 

 bictis Nicholson, Quart. Jour. Geol. Soc. Lond., vol. 30, 1874, 

 p. 507.) (Nicholson, Genus Montic, 18S1, p. 179.) 



Locality. — Warren and Clinton counties, Ohio. 



Remarks. — This is one of the best marked species of the 

 genus, the peculiar rhombic form of the cells serving to dis- 

 tinguish even a small fragment of it. Even when weathered, 

 especially at the ends of the branches, it is immediately rec- 

 ognized. The diagonally-curved arrangement of the calices 

 is another well-marked feature. 



