BRYOZOA. 289, 
Batostoma.] 
by making large collections that the affinities of such species can be determined. 
When this can be done we find that some specimens exhibit, perhaps over limited 
areas only, the full characters of the genus in an indubitable manner. 
The mesopores, therefore, are to be considered as the most unstable feature of 
Batostoma. Though they can never be said to be wanting entirely, it is nevertheless 
true that an inexperienced student might occasionally come to such a conclusion. 
Even in the same species great differences in their number may be encountered. 
Take B. fertile, for instance, in which such deviations are more strikingly expressed 
than in any other species (compare figs. 4 and 7 with 8 and 9 on plate XXV). On 
the other hand the peculiar irregularity of the tubes in the axial region seems 
always to be present, thus assuring us of a clue to the generic affinities of forms 
that, because of the almost total lack of mesopores and practical absence of acan- 
thopores may appear to have relations with types differing widely from Batostoma. 
Respecting the affinities of the species of Batostoma and the systematic position 
of the genus, I have always been in some doubt. At first the Heterotrypide seemed 
the most likely family to receive them, but I soon satisfied myself that their rela- 
tions did not lie inthat direction. Next the Calloporide were suggested, and finally, 
as vol. viii of the reports of the Geological Survey of Illinois was going through the 
press, I decided to place them with the Diplotrypide, and it is with this family that 
I have since arranged them. To-day ano‘her arrangement would suit me better. 
The fact is that most of my time since the printing of the Ilinois work has been 
spent on the Bryozoa, and the last six months were devoted to the Trepostomata 
exclusively. Innumerable comparisons were drawn, many of them resulting in 
important genealogical discoveries. But asis intimated on p. 216, the changes in clas- 
sification that would be necessary, if the results of my comparative studies were 
carried to a logical conclusion, seemed too numerous and great for the present state 
of published knowledge. Indeed, I feared that under the prevailing circumstances 
it would be difficult to substantiate my claims. It should be remembered that 
I work from a basis, or rather with a knowledge of paleozoic bryozoan forms that 
exceeds the published lists by several hundied species. Even with the conservative 
plan adopted by me, I am obliged continually to draw upon unpublished matter to 
prove my points, so that only too often they narrowly escape standing as mere 
assertions. Among other changes that I should have liked to make in the scheme 
of classification on pp. 105-107, is a reconstruction of the families Calloporide, 
Diplotrypide and Trematoporide. In the first place it was a mistake to make 
Trematopora the type of the family as defined, because the relationship to Constel- 
laria, which more truly expresses the characters of the family intended, is yemote 
compared with the affinities existing between Trematopora and Batostoma. The 
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