Geneka of the IsTorth American Palaeozoic Bryozoa. 587 



the centers of which are destitute of cell apertures, and occupied 

 by mesopore apertures. 



Fio. 170. Prasopora conica. Lateral, basal and sectional view of a specimen, natural size. 

 Figs. 171, 172. P. simulatrix. Transverse and vertical sections, xl8. 



DiANULiTEs, Eichwald. 



(Zool. special. Yol. I, p. 180. Dybowsky, Chaetetes d. ost-balt. 

 Siluriform., p. 14. 1877. Syn. Diplotrypa, Mcholson. Pal. 

 Tab. Cor., p. 312. 1879.) 



Type, Dianulites petropoUtana, Eichwald. 



I have been unable to obtain an authentic specimen of the type 

 species, but judging from the published descriptions, its affinities 

 are with the forms included in the family Amplexopobid^. 



Most of the forms described under the name Diplotrypa are 

 not congeneric with the type species. 



Family Calloporidae, Ulrich, emend. 

 The forms included in this family are usually ramose, cells 

 tubular, cylindrical, tabulate ; mesopores more or less abundant, 

 closely tabulate ; interapertural space with pits (mesopore aper- 

 tures). 



