86 BULLETIN 77, UISriTED STATES NATIONAL MUSEUM. 



Genotype. — Crepipora simulans Ulrich. Upper Ordovician (Mays- 

 ville) of the Ohio Valley. 



Crepipora is closely related to the genus Ceramoporella, incrusting 

 forms of the former being very similar to such species as Ceramoporella 

 uxnormensis described on page 82. Perhaps the most obvious generic 

 difference is the practically complete restriction of the mesopores to 

 the maculae in Crepipora, although other equally good characteristics 

 are the more direct zocecial apertures, the better developed maculae, 

 and the greater distinctness of the lunariimi. 



The zoarial growth in Crepipora varies from thin, incrusting sheets 

 to solid massive or hemispherical, and in one case regular hollow 

 branches. The surface shows thin-walled, erect, rhomboidal to polyg- 

 onal zooecia, each having a small but distinct lunarium on the proxi- 

 mal edge. Maculae of mesopores developed at regular intervals are a 

 feature of the surface, where they appear as minutely porous elevations 

 or depressions. In thin sections the maculae and lunaria are most 

 evident, although the ceramoporoid structure described under the 

 discussion of the family is likewise conspicuous. 



At least 15 new or described American species of Crepipora are 

 known, and these, in addition to the three new forms here defined, 

 make the genus one of the more prolific members of the Ceramoporidae. 

 The three Russian forms have little relationship with each other 

 specifically, but are good examples of the range of structure in the 

 genus. The first, C. schmidti, is closely related to the genotype 

 C. simulans, from the middle Cincinnatian strata of the United 

 States, differing particularly in having considerably larger zooecia. 

 The second species is unusual in the irregular angularity of its zocEcia, 

 its very distinct crescentic lunarium, and the unusual development 

 of mesopores. C. incrassata has particularly thick walls, but a quite 

 unusual character seen only in this species, so far as known, is the 

 rounded, ovicell-like structure noted in the thin sections of the type- 

 specimen. 



The occurrence of these cystlike bodies in an undoubted species of 

 Crepipora is of great interest in its bearing upon the zoological posi- 

 tion of the ceramoporoids and related monticuliporoids. These two 

 groups, together with the fistuliporoids, have been assigned to the 

 alcyonarian corals by most writers, but with the present discovery in 

 Crepipora, ovicell-like structures are now known to occur in repre- 

 sentatives of each group. This fact, together with others indicating 

 the bryozoan relations of these disputed organisms, will be discussed 

 in another paper at a later date. 



