EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 227 



This genus as defined by Eichwald is wholly unintelligible and was, until 1877, 

 when Dybowski resurrected and redefined it, not recognized by paleontologists. 

 Dybowski has not helped the matter by his effort, for his arrangement of the species 

 is quite arbitrary, no two forms perhaps being strictly congeneric. 



The only observations of any value at all that have been published 

 concernmg the generic characters of Dianulites are those by Dybowski 

 and by Nicholson. Dybowski retained the genus for those monticuli- 

 poroids in which the zoarium was massive or ramose, and consisted 

 of large, thin-walled, tabulated zooecia in contact with each other 

 on all sides. As expressed in Dybowski's generic synopsis, Dianu- 

 lites would include all forms which have no ''coenenchyma" (inter- 

 stitial cells), but do not possess tabulee in the tubes, which, in addition, 

 are comparatively large and thin walled. Although this limitation 

 of the genus was a distmct advance upon any previous work, still 

 such generic characters were of so little value that, according to 

 present-day studies, Dybowski assigned representatives of at least 

 four other genera to Dianulites. Nicholson, in discussing the sub- 

 genus Diplotrypa^ calls attention to a possible identity between 

 DiplotryjM and Dianulites. However, he rejects the latter name 

 entirely, fu'st, because the generic diagnosis of Eichwald is unrecog- 

 nizable, and, second, because the genus, as resurrected by Dybowski, 

 is unmistakably not a natural group. 



The first species referred by Eichwald to Dianulites was either D. 

 detritus or D. fastigiatus, both of which were described on the same 

 page. Later ^ he distinctly refers to D. detritus as the type species 

 and gives good figures of both D. detritus and D. fastigiatus. The 

 illustrations of these two forms are clearly of the same species, and 

 their identity was recognized by Dybowski, who, however, figures 

 and describes the species as D. fastigiatus. As I have not had the 

 opportunity of consulting the original publication, and as Dybowski 

 was probably able to do so, I have accepted the specific naiae fastigi- 

 atus for the genotype, Smce both names apply to the same form, 

 the matter is of little consequence. 



The external features of Dianulites fastigiatus are so unique that a 

 study of the internal structure is not necessary to determine the 

 species. Indeed, the merest tyro could identify the species from 

 Eichwald' s figures, one of which shows clearly that the zooecia are 

 completely isolated by mesopores. The occurrence of numerous 

 mesopores is corroborated by thin sections, and yet Dybowski laid 

 stress upon the absence of mesopores, or, in his words, the absence of 

 coenenchyma, as a generic character. 



After studying specimens of Dianulites fastigiatus from six Kussian 

 and Swedish localities, I find that this species, as well as a number of 



1 Genus Monticulipora, 1881, p. 155. 



a Lethsea Rossica, vol. 1, 1860, p. 487, pi. 28, figs. 8, 9. 



