CAMBRO SILURIAN MICRO- PALiEONTOLOQY. 



DESCRIPTIONS OF SPECIES. 



T. On the AloniicuUpondce of the Chazy, Black liiver, and Trenton Forma- 

 tionSf with descriptions of ten new species. 



MoNTICULIPORA, D'Oibigny, (restricted); 



^^ External Characters, — Zoarium massive, lobatc, laminar, incrusting, and 

 sometimes irregularly frondescent. Surface sometimes smooth, usually 

 tuborculated. Monticules closely approximated, usually conical, often 

 elongated or compressed. Cells small, their diameter varying in different 

 Fpecics from -^^ ^^ xio ^^ ^^ inch, polygonal, and with thin walls ; gen- 

 erally groups of cells slightly larger than the average are distributed at 

 regular intervals among those of the ordinary size. Not infrequently a 

 few smaller (young ?) cells occupy the summits of the monticules, and 

 they may occasionally bo 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 diajihragms; and often there are 

 lai"go cystoid diaphragms present. In the mature zones the walls become 

 very slightly thickened, and small spiniform tubuli can usually bo 

 detected; while numerous cystoid diaphragms are always developed in 

 the greater number of the tubes. Immediately above the point of gem- 

 mation, the young tube is crossed by numerous straight diaphragms giving 

 it the appearance of an interstitial tube. Subsequently 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 

 licights may show in one comparatively numerous small tubes, intercalated 

 among the ordinary cells, while another may show but few or none of 

 them. Trenton and Cincinnati." (E. O, Ulrich, Journ. Cincinnati 

 Soc. of Nat. Hist., Vol. V., p. 232, 1882.) 



MONTICULIPORA WeSTONI. (N, Sp.) 



Plate L, figs. 1, la, 16. 



Zoariiim irregularly hemispherical. The only specimen collected, which 

 Is very imperfect, measures from 20 to 25 mm. in its greatest diameter, 

 and about 15 mm. in thickness. Surface studded with small and incon- 



