PROBLEM OF THE MONTICULIPOROIDEA I I 



side to the convex upper one, the lower side being covered, if 

 well preserved, by a thin "epitheca" or coating produced by no 

 one zooid, but by the cortex uniting all. The growth of the 

 epitheca was, of course, marginal. At this margin, close on the 

 epitheca, there was rapid budding of young cells, some of which 

 became quickly full-sized ; others became mesopores. At the 

 periphery the cells open obliquely to the zoarial surface. Above 

 it all apertures are more direct. 



The number of mesopores in this species (PI. A, Fig. 8) is 

 so far greater than that of the autocells that relatively few of 

 them can become autocells. They are fewest proportionally in 

 maturer zoaria, and appear to be homologous with those of 

 Diplotrypa, only smaller, longer, and, so to say, more perma- 

 nently mesopores. The numerous small, angular, or impressed 

 mesopores, with shallow openings or calycals, surround the 

 rounded apertures of the thick-walled autocells, making an 

 easily recognized figure at the surface. At intervals occur clus- 

 ters of cells larger than the average, with more numerous 

 mesopores between them, and thicker walls. They form low 

 monticules, or on weathered specimens high ones. They are 

 areas of rapid cell increase. 



The mesopores have numerous transverse tabulae (PI. A, 

 Fig. 9) . Those of the autocells are numerically proportional, 

 considering the cells' size, but they curve obliquely across, or 

 oftenest form cystiphrams, i, e., the tabulae in the most regular 

 instances are narrowly beaker-shaped, and are arranged in the 

 cell as nested equal-sized beakers could be in a tube. The flat 

 bottoms have been called diaphragms or tabulae, the sides cysti- 

 phrams. Often the cystiphram extends only partly around the 

 cell, and partly the same lamina is incorporated with the cell 

 wall. Cystiphrams appear to indicate that the zooid body with- 

 drew simultaneously, or nearly so, from the calycal bottom and 

 side, or sides, near the bottom. 



The cell wall margins here were not all straight since, acan- 

 thopores occur. These are minute wart-like structures or thick- 

 enings on the cell wall margins, especially at angles, and were 



