212 SYSTEMATIC PALEONTOLOGY 



than the other. Measuring longitudinally the former has four and one- 

 half zooecia in 2 mm., the other only three and a half. Diagonally one 

 has six, the other five in the same space. Thickness of zooarial sheet 

 not exceeding 0.2 mm. 



Membranipora perampla Gabb and Horn, which occurs rather fre- 

 quently in the Upper Cretaceous at Vincentown and other points in New 

 Jersey, sometimes resembles this species, but its zooecia are larger, less 

 regular, with irregular spaces often between the rims and one side of 

 the latter generally higher than the other, while none of the covered 

 cells described above have so far been observed in it. The zooecia are 

 more regularly arranged in M. rimulata than in any of the simple spe- 

 cies of the genus known to the writer, and this fact, together with the 

 presence of the peculiar covered cells, is principally relied upon in dis- 

 tinguishing the species. Two fragments in my collection of Cretaceous 

 bryozoa found at Vineentown, IS]". J., and regarded as Biflustra disjuncta 

 Gabb and Horn, have very similar covered cells, and, considering the 

 variations shown in my specimens of this species, seem to show a closer 

 relation to M. rimulata than to any other form. 



Occurrence. — Aquia Fokmation. Upper Marlboro. 



Collection. — Maryland Geological Survey. 



Membeanipoea spiculosa n. sp. 



Plate LX, Figs. 3, 4. 



Description. — Zoarium adnate. Zooecia arranged in quincunx or ir- 

 regularly, oblong, rounded and widest above, more or less produced be- 

 low. Opesia large, normally ovate, the upper edge nicely rounded, the 

 lower variable, taking up about half of the length of the zooecium. 

 Rim thin, highest above, usually dying out before reaching lower ex- 

 tremity of zooecium. Front wall over lower half of zooecium, slightly 

 depressed, covered with small granules or spines, those bordering the 

 edge projecting sharply into the opesial opening. Ooecia numerous, 

 cueullate, strongly elevated, often with a tubercle or point forming the 

 summit. When a zooecium is without an ooecium its place is often oc- 

 cupied by an elevated avicularium of moderate size. The avicularia 

 are very few in number but when present similar to those found in Eepto- 



