. Bulletin - United States National Museum. Science. 124 BULLETIlsr 77, UNITED STATES NATIONAL MUSEUM. and more complete specimens preserving the pointed base are by no means rare. Although Eichwald gives but a single illustration of the species, a view, natural size, of a zoarium preserving the pointed base (fig. 49 a), there can be little question that his type of Coscinium proavus and the specimen figured in the present work are identical, mainly because Graptodictya proava is the only known cribrose Mid- dle Ordovician Russian bryozoan with the pointed base and dimen- sions shown in his fi
. Bulletin - United States National Museum. Science. 124 BULLETIlsr 77, UNITED STATES NATIONAL MUSEUM. and more complete specimens preserving the pointed base are by no means rare. Although Eichwald gives but a single illustration of the species, a view, natural size, of a zoarium preserving the pointed base (fig. 49 a), there can be little question that his type of Coscinium proavus and the specimen figured in the present work are identical, mainly because Graptodictya proava is the only known cribrose Mid- dle Ordovician Russian bryozoan with the pointed base and dimen- sions shown in his figure. This same species has been found in American strata, as determined from my study of the specimen (see fig. 6, pi. 9) which Sardeson, in his ''Problem of the Monticuli- poroidea"^ figures and describes at length under the name of Stic- toporella cribrosa Ulrich. In spite of Sardeson's statement to the contrary, it is a fact that species of Stidoporella have an expanded incrusting base and never have a pointed base for articulation. Com- parison of figures of both species here pre- sented can not fail to convince the discrimi- nating person of numer- ous zoarial and zooecial differences between Stictoporella crilrosa Ulrich and Graptodictya proava. Indeed, ob- servers who have had opportunity to study numerous examples of these several types of structure, assign them to separate families, as in the present work. Graptodictya proava is known from a second American locahty, namely, along the Escanaba River in Mchigan, below the upper falls. A fine, large example from this place was made the type of Hall's ClatJiroporaflaheTlata. Through the courtesy of Dr. E. O. Hovey, of the American Museum of Natural History, I have had the opportunity of studying this type and of presenting an illustration of its minute structure to show the specific identity. The specimen itself has been broken out of the sohd limestone and thus is parted along the mesial lamina. Its cribrose zoarium
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