1 62 FREDERICK IV. SARDESON 



Secondary and tertiary segments are similar to primary ones 

 partly developed. 



A related genus, Arthrostyltis, has the segments with four sides, 

 one of which is without cell apertures but striated. 



Rlwmbopora lepidendroid.es Meek, is strictly a cylindrical type. 

 A small, thin basal expansion supports a long, branching, cylin- 

 drical stem about 2 mm in diameter. There is a central thin-walled 

 axial region in which the polygonal cells may have one tabula, 

 and there is a narrow, thick-walled peripheral region with narrow 

 cell openings without tabulae. The surface shows oval cell aper- 

 tures at the center of calycals, these being arranged in transverse, 

 vertical, and oblique rows, their margins being more or less in 

 contact. The elevated interspace has rows of small warts, which 

 divide the zoarial surface somewhat into rhombs, including each 

 a calycal. Usually a second larger set of warts or acanthopores 

 are situated at the junction of the rows. The internal wall 

 structure corresponds, i. e., the thin, dense walls of the axial 

 region change quickly to thick in the peripheral region, with 

 striation parallel to the calycal, interspace, and wart surfaces. 



There is no distinct evidence of mesopores, but a simulation 

 of maculae and other characters in common with the forms of 

 Trepostomata, genera Batostomella, Eridotrypa Batostoma, which 

 they approach more closely than to other than cylindrical Crypto- 

 stomata, would indicate that the interspaces are mesopores rather 

 than thickened autocell walls alone. 



Phylloporina corticosa Ulr. belongs to the reticulate series, and 

 has a reticulate frond and solid basal expansion (Plate B, Figs. 1 1 

 and 12). The frond is composed of so-called branches 0.5 to 1 

 or 2 mm wide, which anastimose laterally at somewhat regular 

 intervals, producing elongate fenestrules. Each branch has cells 

 on the obverse side, but none on the solid, smooth or striated 

 reverse side. Thin sections show that the cells arise mesially, 

 have a long, thin-walled, tabulated prostrate portion, then become 

 more closely tabulated as they turn slowly into the peripheral 



