EAELY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 253 



ORBIPORA DISTINCTA (Eichwald). 



Plate 3, figs. 10-lOb; text figs. 144-147. 



Orhitulites distinctus Eichwald, Zool. spec, vol. 1, 1829, p. 180. 



Favosites hemlsphsericus Kutorga, Beitrag zur Pal. Dorpats, 1835, p. 40, pi. 8, 



figs. 5 a-c (not pi. 9, fig. 3). 

 Orbipora distincta Eichwald, Bull. Soc. Nat. Moscou, No. 1, 1856, p. 93; Letligea 



Rossica, vol. 1, sect. 1, 1860, p. 484, pi. 28, figs. 6, 7 a-c— Dybowski, Die 



Chsetetiden der Silur-Formation, 1877, p. 60, pi. 2, figs. 10, 10a, 106. 

 Chaetetes hemisphaericus Eichwald, Lethsea Rossica, vol, 1, sect. 1, 1860, p. 476, 



pi. 28, fig. 5. 



The general ciiaracters of this species have been mentioned in the 

 discussion of the genus, but these, as well as the more specific points, 

 are given in the following diagnosis. 



Zoarium consisting of a flattened, 

 discoidal mass, sometimes as much as 

 40 mm. wide and 7 mm. in its greatest 

 height, flat or slightly concave and 

 covered with a wrinkled epitheca on 

 its lower side, slightly convex on the 

 upper or celluliferous surface. Maculae 

 either absent or differing so little from 

 surrounding areas that they are indis- 

 tinguishable. The surface is without 

 monticules or elevations of any sort, but 

 is roughened by numerous sharp acan 

 thopores. Zooecial tubes large, polyg- 

 onal, usually hexagonal, varying from 0.8 mm. to 1.0 mm. in diameter. 

 Mesopores absent entirely. Acan thopores numerous, as many as 16 

 surrounding a single zooecium. 



Fig. 144. — Oebipoea distincta. a and b, 



BASAL AND CELLUUFEKOUS SIDES OF A 

 YOUNG ZOAErUM,NATURAL SIZE, DESCEIBED 



BY Eichwald as Chaetetes hemispher- 

 icus; c, side view of the same specimen; 

 d, cellulefeeous sitkface enlaeged. 

 "Calcaiee a. Orthoceratites," Pul- 

 kowa.goveenmentofSt. Petersburg. 

 (After Eichwald.) 



Fig. 145.— Orbipora distincta. o and 6, top and side views, natural size, of one of Eichwald'3 

 type-specimens of Orbipora distincta; c, celluliferous face enlarged; d, woen poetion of 



ZOAELA.L base ENLARGED; e, VEETICAL SECTION; /, g, AND ft, VIEWS OF A LAEGER EXAMPLE REFERRED 

 TO THE species; i, SIDE VIEW OF ZOCECIAL TUBES, "CALCAIEE 1 ORTHOCERATITES," PULKOWA AND 



AVesenberg. (After Eichwald.) 



The internal characters of a well preserved specimen are shown in 

 figures 146 and 147. In tangential section fhe numerous large acan- 

 thopores are particularly noticeable. Here also the rather large 



