234 



Cincinnati Society of Natural History. 



that the name Homotrypa (as defined further on) be accepted for the 

 group of species which nry unfortunate mistake led me to believe to be 

 congeneric with Hall's Trematopora tuberculosa. 



Monticulipora mammdlata, D'Orb. (Plate X., figs. 5, 5a.) 



Monticulipora mammulata, D'Orbigny. Prodi*, de Paleont., vol. 1, 

 p. 25, 1850. 



Chwtetes mammulata, Edwards and Haime. Pol. Foss. des Terr. 

 Pal., p. 267, Plate XIX., fig. 1, 1851. 



Monticulipora mammulata, Edwards and Haime, Brit. Foss. Cor. 

 p. 265, 1854. 



Mo?iticulipora (Peronopora) molesta, Nicholson. The Genus 

 Monticulipora, p. 224, Plate VI., figs. 2, 2d. Not Monticulipora mam- 

 mulata, Nicholson. 



Zoarium occurring as irregularl}' lobate masses, often of considerable 

 size, that usually tend to throw off compressed processes, which in 

 many specimens become frondescent; or, it may take the form of 

 extended and undulated, often palmate, expansions, varying in thick_ 

 ness from 2 inch to .4 or .5 inch. Surface covered with numerous 

 prominent, t} r picairy conical, often elongated monticules. The last 

 feature is produced by the fusion of two or three of them. They are 

 quite regularly arranged in series, in which sometimes five, usually, 

 however, six, may be counted in the space of .5 inch. Cells polygonal, 

 thin-walled, subequal, from -3-J-oth to -5-g-oth inch in diameter,* those 

 occupying the summits of the monticules, being scarcely larger than 

 those in the Intervening spaces. Smaller or interstitial (?) cells may 

 occasionally be observed, more frequent^ on the monticules where 

 they are wedged in between the ordinary cells. When the cell walls 

 are perfectly preserved, they show the spiniform tubuli as minute 

 granules. 



Longitudinal sections show conclusively that the zoarium is divided 

 into successive " immature" and "mature" zones. In the first, the 

 cell-walls are very thin, and the tubes are almost invariabty crossed 

 only by straight or somewhat obliquely directed diaphragms, at 

 distances apart of about one tube-diameter. This zone is very uarrow, 

 and soon a ''mature" zone is entered when the walls are slightly 



* In all cases where the diameter of a cell is given, the measurement includes the wall. 

 The dimensions given were obtained by calculating the number of cells in a given space. 

 For instance, if the diameter of the cells of a species is stated to be l-100th of an inch, it is 

 equivalent to saying that ten cells may be counted in the space of one tenth of an inch. 



