EARLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 835 



Gothland, where the name Callopora nana has been appHed to it by- 

 Nicholson. The Russian specimens were derived from the Lyckholm 

 limestone (Fl), Kertel, island of Dago (Cat. No. 57474, U.S.N.M.), 



Fig. 210.— Hallopoba elegantula. a, tangential section, X18, with three of the zocecia show- 

 ing opercula; 6, transverse section, X18, illustrating the sh-u-e of the zocecia and mesopores 

 m the immature region; c, tangential section, X20, through the mature zone; d and e, two 



VERTICAL sections, X18 AND X20, SHOWING SLIGHT DIFFERENCES; /, SURFACE VIEW OF SEVERAL ZOOECLA, 

 X20, SHOWING PERFORATED CLOSURES. NUGARAN (ROCHESTER SHALE), LOCKPOKT, NeW YoRK. 



and the Borkhohn limestone (F2), at Borkhohn, Esthonia (Cat. No. 

 57475, U.S.N.M.). 



Specimens from American localities in the British Museum. 



HALLOPORA ? DYBOWSKU, new species. 

 Plate 5, figs. 1-lZ; text figs. 211, 212. 



Callopora nummiformis Dybowski (part), Chaetetiden der Ostbaltischen Silur- 

 Formation, 1877, p. 109, pi. 4, figs, la-l (part). — Nicholson, Man. of Paleon- 

 tology, 1889, p. 348. 



Not Callopora nummiformis Hall, Nat. Hist. New York, Pal., vol. 2, 1852, p. 148, 

 pi. 40, figs. 5, 5a. 



Associated with Diplotrypa petropolitana in the Kussian and 

 Swedish Middle Ordovician formations is a hemispheric bryozoan so 

 similar in almost all respects that an examination of a vertical sec- 

 tion or fracture is necessary to distinguish it. This new species is 

 quite as abundant as its associate and the most conspicuous differ- 

 ence, without the examination of thin sections, is in its sparing devel- 

 opment of diaphragms. Under the name of Callopora nummiformis 



