EAELY PALEOZOIC BKYOZOA OF THE BALTIC PROVINCES. 313 



In other words, the genus is Hke Monotrypa save that mesopores are 

 present. 



Genotype. — Diplofrypa petropolitaTia Nicholson. Middle Ordovician 

 of Baltic Russia and Sweden. 



DIPLOTRYPA PETROPOLITANA (Nicholson). 



Text figs. 192-195. 



Monticulipora (Diplotrypa) petropolitana Nicholson, Pal. Tab. Corals, 1879, p. 

 313, pi. 13, figs. 3-3 c; The Genus Monticulipora, 1881, p. 156, text fig. 30. 



The following may also be included, at least in part, in the present 

 species: 



Millepora TiemispTienca (part) Eichwald, Inter ingrica et de trilob. observat., 



1825, p. 21. 

 Favosites petropolitanus Pander, Beitr. zur Geogn. d. russ. Reiches., 1830, p. 105, 



pi. 1, figs. 7-11. 



Fig. 192.— Diplotetpa peteopolitana. Nicholson's illustrations of Monticxilipoea (Diploteypa) 

 petropolitana, introduced for comparison. a, profile view of an average specimen, 



NATURAL size; b, BASAL VIEW OF SAME SHOWING WRINKLED EPITHECA; C, TANGENTIAL SECTION, X20; 

 d, VERTICAL SECTION THROUGH AN IMMATURE AND A MATURE ZONE, X20. MIDDLE ORDOVICIAN (CHAS- 

 MOPS) LIMESTONE, OSTROGOTHIA, SWEDEN. 



Favosites hemisphericum Kutorga, Beitr. zur Paleontologie und Geogn. Dorpats, 

 1837, p. 40, pi. 9, fig. 3. 



Calamopora fibrosa Eichwald, Silur. syst. in Ebstl., 1840, p. 197. 



Chxtetes petropolitanus Lonsdale, in MurcMson, Verneuil, and Keyserling, Russia 

 and Ural, vol. 1, 1845, p. 596, pi. A, fig. 10. — Keyserling, Raise in d. Pet- 

 scboraland, 1846, p. 180.— D'Orbigny, Prodr. de Pal., vol. 1, 1850, p. 25.— 

 Edwards and Haime, Mon. des Pol. foss., 1852, p. 263. 



Monticulipora petropolitana Edwards and Haime, Brit. Foss. Cor., 1854, p. 264. — 

 Schmidt, Archiv fur Naturk. Liv.-, Ehst- u. Kurlands, vol. 2, eer. 1, 1858, 

 p. 228. 



Not Dianulites petropolitanus Dybowski and other authors. 



Zoarium massive, discoid when young but with age becoming hemi- 

 spheric to spheroidal; base circular, often concave and covered with 



