BRYOZOA. 471 



CREPIPORA EPIDERMATA Ulrich. 



PL XL, Fig. l-le. 



Zoarium forming a subcircular undulating expansion, attain- 

 ing a diameter of eight cm. or more: the thickness varies from 

 two to eight mm. Upper surface with slightly elevated large 

 macula? of mesopores. varying both in size and arrangement; 

 usually about four or five mm. apart. Apertures directed out- 

 ward from the center of the zoarium, the lunarium being moder- 

 ately conspicuous, with no striking regularity of arrangement, 

 sub-circular to sub-triangular, 0.4 to 0.6 mm. in diameter: 

 about six in three mm. Zooecial tubes with walls rather thin 

 throughout, very soon after their origin proceeding almost 

 direct to the surface. Usually a single diaphragm is developed 

 in each tube. Lunarium occupying about one-third of the wall, 

 with a radial structure as shown in fig. le, pi. XL. Mesopores 

 abundant, variable in shape and size, scattered about among 

 the zocpcia, but mainly gathered into clusters of fifteen to fifty: 

 very irregular in vertical section, sometimes provided with a few 

 diaphragms. 



The form of the zoarium, the structure of the lunarium, and 

 certain peculiarities of the mesopores, suggest affinities with the 

 FISTULIPORID.E. Specifically it is widely different from all the 

 other species of the genus excepting C. squamata (Discopora 

 xqnamata Lonsdale.) from the Upper Silurian rocks of England 

 and Gotland. The European form differs in several respects, 

 such as having the macula? smaller and the zooecia apertures 

 more oblique. The zoarium is also less robust. 



Position and locality: Cincinnati group; common at Wilming- 

 ton, 111. 



CREPIPORA IMPRESSA Ulrich. 



PL XL, Fig. 2-2a. 



This species, which has all the characters of the genus, is 

 chiefly distinguished by having exceptionally conspicuous lunaria, 

 and large sized, but irregularly distributed maculae, depressed below 

 the general level of the surface. The single specimen seen is 

 an elongated, hollow stem four cm. long by six mm. in aver- 



