On the Montiailiporoids of the Cincinnati Group. 175 



Corallum dendroid, branching dichotomously, branches vary- 

 ing from less than one line to two lines in diameter. Surface 

 smooth, calices generally oval, long axes corresponding to the 

 long axe^ of the branches; of two kinds, the larger separated by a 

 considerable number of interstitial tubes. Walls thickened at cell 

 mouths. Operculae often closing apertures of cells. 



Obs. This species is characterized by the peculiar habit of 

 growth, branching in a very irregular manner at almost every pos- 

 sible angle and anastomosing so as to form various shaped figures ; 

 by the presence of a considerable number of interstitial corallites 

 between the larger ones, and a generally smooth surface. 



Formation and Locality. Lower Silurian, Cincinnati Group, 

 Cincinnati, O. 



20. M. COMMUNIS, James. 



Monticulipora {Hderotrypa) d" neaUi i^) var. communis, James. 

 The Palaeontologist, 47, 1882. 



Callopora subplana, Ulrich. Jour. Cin. Soc. Nat. Hist., V., 

 253. 1883. 



Corallum dendroid, but as generally found, much broken, 

 the cylindrical or sub cylindrical stems from one to three lines 

 in diameter, branching at variable distances at acute angles, but 

 masses of considerable size — from one inch to six or eight inches 

 or more in diameter — sometimes found, in which the stems 

 anastomose in a very irregular manner. The surface of most speci- 

 mens with maculse or monticules, raised little or not at all above 

 the surface, occupied by calices much larger than the average, 

 and sometimes clusters of smaller tubules. Calices oval or sub- 

 circular, occasionally somewhat angular; interstitial corallites 

 numerous, occasionally nearly or quite surrounding the larger cells, 

 and of various shapes; about six calices in the space of one line in 

 the longitudinal direction of the stem, and seven or eight trans- 

 versely Cell walls thin at the surface of unworn specimens, but 

 thickened immediately below. (Plate 2, figs, ^a, b, e. ) 



Obs. At the time of making the original description of this 

 species, the writer believed it to be, probably, a variety of M. 

 o'nealli, but on further examination of many specimens, he has 

 come to the conclusion that it is worthy of a distinct name. Some of 

 the main points of difference are the much larger calices in the 

 maculae, the greater number of small corallites between or surround- 



