32 F. A. SMITT, 



The primary aperture of the one I measured to be of about 0,09 min. in the breadth, 

 what is only two thirds of the usual size in the northern specimens of Anarthropora 

 minuscula. For its further investigation it may retain its separate name. 



Tessaradoma boreale *) (Pl. VI, tigs. 143 — 145). 



If we accept the Normannian genus Anarthropora for expressing the celleporine 

 tendeney of the Porinidan type, such as this is represented by Porina violacea, we 

 must, of consequence, do the same with his genus Tessaradoma, which is nothing else 

 than the same change of the named type, such as we have seen it in the Porina ser- 

 rulata. Still, as these two Porina? scarcely will be separated in different genera — 

 for, in consequence of such an opinion, we should soon, I fear, have as many genera, 

 as we have species — then, the systematical value of Tessaradoma, as well as of 

 Anarthropora, is very problematical. Furthermore, with our present knowledge of the 

 bryozoa, for the definition of that genus, it will scarcely suffice to cite the characte- 

 ristic, given by Saks and translated in English by Ålder. 



The Tessaradoma boreale, after Pourtales' collections, seems to be one of the 

 inöst common Floridan Bryozoa. At twenty different localities, in well developed co- 

 lonies, he has taken it living at the depths of from 82 to 450 fathoms. In the same 

 manner it is not uncommon in the deep-water on the European side of the Atlantic, 

 from Spitzbergen to the West off Portugal and at the Azores 2 ). 



With the richness of the specimens it has been possible to follow its develop- 

 ment from the creeping state, which, without doubt, would have been referred, by the 

 authors, to a different family. The one of these colonies ffig. 143), then, would have 

 been a Lepralia; the other (fig. 144), in its beginning, should have been named Alysi- 

 dota, but it grows into the constitution of a Lepralia, and thence it raises itself to the 

 wellknown Tessaradoma boreale. May this be a neAv warning against the constitution 

 of families and genera only after the form of the colonial growth! 



At the side of the Porina? I have placed the 



MYRIOZOHXE 3 ), 



which, in their most typical constitution of the zooecia, in a very pregnant manner 

 remincl us of the Porinw, as the median pore of these is represented, in the Myriozoids, 

 by the median sinus of the proximal margin of the aperture. But all the variations, 

 as well as the developmental changes of the typical Myriozoidoe, have caused us to 

 conjoin very different forms into the limits of this family. For the more complete 

 discussion of these relations I must refer the reader to my papers on the scandinavian 



x ) Synon. vide Krit. Fört., Öfvers. Vet. Akad. Förh., 1867, Bih., p. 8. 



Adde: Tessaradoma gracile, Norm., Brit. Assoc. 1868, Rep., p. 309. 



2 ) Attending to this great geographieal distribution, it would be of interest to compare it with the Cretacean 

 fossil, Porina filiformis, D'Orb. (Pal. Franc., Terr. Crét., vol. V, pag. 438, pl. 714, figs. 11— 13), because, 

 with the exception of the compressed form of the branohes of that species, we can scarcely see, with 

 certainty, any speeifical distinction, as the small avicularia verv easily can have escaped the observation. 



3 ) Öfversigt Vet. Akad. Förh. 1867, Bih., p. 8. 



