232 



Cincinnati Society of Natural History. 



AMERICAN PALAEOZOIC BRYOZOA. 

 By E. O. Ulrich. 



[Continued from Vol. o, page 275.] 



Monticulipora, D'Orbign}- (Restricted). 



Monticulipora. D'Orbigny, Prodr. de Pal., vol. 1, p. 25, 1850. 



External characters. — Zoarium massive, lobate, laminar, incrusting, 

 and sometimes irregularly frondescent. Surface sometimes smooth, 

 usually tuberculated. Monticules closely approximated, usually coni- 

 cal, often elongated or compressed. Cells small, their diameter var} r - 

 ing in different species from g^th to y^th of an inch, poh'gonal, and 

 with thin walls; geuerally groups of cells slightly larger than the 

 average, are distributed at regular intervals among those of the ordin- 

 aiy size. Not infrequently a few smaller (3 T oung ?) cells occupv the 

 summits of the monticules, and the} 7 ma} r occasionally be detected 

 between the cells occupying the hollow interspaces. 



Internal characters. — Tubes in the "immature" zones, with very 

 thin walls, and crossed by straight or oblique diaphragms; and often 

 there are large eystoid diaphragms present. In the mature zones the 

 walls become very slightly thickened, and small spiniform tubuli can 

 usually be detected; while numerous eystoid diaphragms are always 

 developed in the greater number of the tubes. Immediately above the 

 point of gemmation, the } T oung tube is crossed by numerous straight 

 diaphragms, giving it the appearance of an interstitial tube. Sub- 

 sequentl}' the diaphragms become less crowded, and the young tube 

 assumes the characters of an ordinary cell. The process of gemmation 

 seems to have taken place more especially at certain levels, since 

 tangential sections taken at different heights, may show in one com- 

 paratively numerous small tubes intercalated among the ordinary cells, 

 while another may show but few or none of them. 



The genus Monticulipora as above defined and restricted, includes, so 

 far as I have been able to ascertain, no less than ten distinct species, 

 nine of which belong to the Cincinnati Group of Ohio and Kentucky, 

 and the tenth to the Trenton Group of the latter State. Of these, 

 two have been already published, the t}-pe species, M. mammulata, 

 D' Orb., and the 31. cincinnatiensis, James (as fig. and described b\- 

 Nicholson), four I now publish for the first time, 31. Iceuis, 31. con- 



