322 THE PALEONTOLOGY OF MINNESOTA. 
(Crepipora. 
Genus CREPIPORA, Ulrich. 
Crepipora, ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 157; 1890, Geol. Surv. Tll., vol. viii, 
pp. 380, 469. 
Zoaria incrusting, massive, or hemispherical; in one case forming regular hollow 
branches. Surface, especially in the first and last styles of growth, exhibiting at 
regular intervals macule of mesopores, appearing as minutely porous or subsolid 
elevations or depressions. In the massive forms these macule, to which the meso- 
pores are usually restricted, are very small. Zoccial tubes erect, their apertures 
very slightly oblique and varying from rhomboidal to subpyriform in shape. Luna- 
rium small and easily overlooked except in well preserved examples; best shown in 
tangential sections. Thin diaphragms are developed in moderate numbers. 
Type: C. simulans Ulrich. 
Eleven or twelve species, several as yet undescribed, are known to me having 
the characters ascribed to this genus. Three of these are Trenton, the rest, save an 
Upper Silurian species from Gotland, are Utica or Hudson River group forms. 
Crepipora differs from Ceramporella in having much fewer mesopores (typically 
none) in the inter-macular spaces, longer tubes, and less oblique apertures. C. epi- 
dermata Ulrich, from the Hudson River group of Illinois, is closely related to the new 
genus Bythotrypa, and ought perhaps to be referred to that genus, but it has seemed 
the wiser course to leave the species as originally described until special investiga- 
tions into the inter-relations of the Ceramoporide can be taken up. 
\CREPIPORA SUBHQUATA, 2. Sp. 
PLATE XXVIII, FIGS. 26-28. 
Zoarium a small laminar or incrusting expansion, 1 to 3 mm. thick. Zocecial 
apertures approximately direct, angular, often quadrate or pentagonal, of nearly 
uniform sizes on all parts of the surface, no distinguishable clusters of cells larger 
than the average having been developed; ten in 3 mm. Lunarium very slightly 
developed, the zocecial apertures and walls appearing much more like those of 
species of Monotrypa than of aceramoporoid. Tangential sections, however, (see figs. 
26 and 27) afford more or less clear evidence of its presence, but it is rare to find 
more than one of the ends of the lunarium projecting inward from the wall. Many 
of the angles of junction are thickened and include an acanthopore-like structure. 
