NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
5 
at present study these interesting animals. The paleontologist who has not followed 
closely the development of all these researches and who is not himself a trained 
zoologist is absolutely powerless to prepare a useful work. On the other hand, a 
large paleontologic work prepared by a competent zoologist would be little com- 
prehended by the readers, since they have not been able to study any comprehensive 
work embodying the more important progress in bryozoology. 
The present writers were therefore in a quandary since by preparing a strictly 
paleontologic monograph they ran the risk of publishing a work incomprehensible 
and discouraging to students and collectors alike. In order to avoid such a result 
they decided to closely associate the paleontology and zoology of the bryozoa by 
the introduction of numerous text figures, wherein the more recent work concern- 
ing each of the families and genera considered is illustrated. Naturally this is not 
as comprehensive a zoologic work as could be desired, but it is sufficient for the 
exact interpretation of the structure of the Tertiary bryozoa of American strata. 
This has been supplemented by lists of recent and fossil species under each genus. 
No attempt has been made to classify all the known species, but the lists are simply 
complete enough to remain exact. 
The terminology of the bryozoa has become somewhat specialized, although it 
is still far from being very complicated. The reader will easily become familiar 
with it by the aid of the special drawings scattered among the text figures. 
Although the Tertiary bryozoans often occur literally by the million in a 
stratum, they are usually so inconspicuous as to be unnoticed by the average 
collector. When these fossils are present a careful examination of a weathered 
outcrop will almost invariably reveal a few minute twig-like stems or porous, 
flattened fragments projecting from the surface. Further search along the outcrop, 
especially along a seam in the rock, is very liable to result in the discovery of many 
such fragments. 
As most of the American Tertiary bryozoa occur in soft limestone or marls, 
the collection of the material for study consists simply in scooping up a large 
amount of the loose rock containing these fragmentary remains. If the specimens 
are found in a hard, indurated rock, it is usually only a matter of search to find 
a spot where the matrix has decomposed, leaving the soil filled with free specimens. 
In any case it is not advisable to pick up the specimens one by one, not only on 
account of loss of time, but also of breakage. On arriving at the laboratory the 
clay or other rock holding the bryozoans should be allowed to soak in water for 
some hours. The material may then be agitated and the muddy water poured 
away. Continuing this process until the agitated water no longer becomes muddy, 
the residual mass is set aide to dry. The debris when dry is then ready for 
assorting, although passing it through several sieves of different mesh greatly 
facilitates the assorting of the contained fossils. 
When bryozoa are quite rare in any exposure it is well to do most of the 
sieving in the field if possible. For example, the interesting lowest Eocene fauna 
secured at Upper Marlboro, Maryland, was collected only after several days’ active 
