Batostoma.l BEYOZOA. 289 



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 Heterotrypidce seemed 

 the most likely family to receive them, but I soon satisfied myself that their rela- 

 tions did not lie in that direction. Next the Calloporidce 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 Diplotrypidce, and it is with this family that 

 I have since arranged them. To-day another arrangement would suit me better. 

 The fact is that most of my time since the printing of the Illinois 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 as is 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 gteat 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 hundred 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 Calloporidce, 

 Diplotrypid(B and Trematoporidce. 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 remote 

 compared with the affinities existing between Trematopora and Batostoma. The 



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