EARLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 145 



Wiman's figures, here reproduced, represent a species of Pachydidya 

 with surface characters identical with P. hifurcata. Young specimens 

 of P. hifurcata in the collection from the Borkholm limestone at 

 Borkholm have considerable similarity to Wiman's figured examples, 

 and this leads me to believe in the identity of the two species. 



Occurrence. — Abundant in the Silurian (Clinton) limestone at 

 Dayton and other localities in Ohio and Indiana. Equally abundant 

 in the Lyckholm limestone (Fl) at Kertel, on the island of Dago, and 

 at Lyckholm, Esthonia; in the Borkholm hmestone (F2) at Bork- 

 holm, Esthonia; Borkholm drift, Ojle Myr, island of Gothland. 



Plesioty pes. —Csit. No. 57240, U.S.N.M. 



Specimens from the Borkholm hmestone, Borkliolm, Esthonia, and 

 from the Lyckholm limestone, island of Dago, in the collections of 

 the British Museum. 



Family CYSTODICTYONID^ Ulrich. 



No genus of tliis family has hitherto been recorded from rocks 

 older than the Middle Devonian, yet a single specimen from the 

 Orthoceras hmestone on the island of Rogo possesses all the char- 

 acters of typical Ooscinium. The Cystodictyonidse in all probability 

 are derived from the Rhinidictyonidse, from which they differ most 

 conspicuously in having a more or less well developed lunarium. It 

 is possible that this appearance of Ooscinium in the Mddle Ordovician 

 represents an early expression of this fine of descent and that the 

 characters were still too unstable to survive for any time. 



' Genus COSCINIUM Keyserling. 



Cosdnium Keyserling, Reise in das Petschora Land, 1846, p. 191. — Prout, 

 Trans. St. Louis Acad. Sci., voL 1, 1858, p. 266. — Ulrich, Joiirn. Cincinnati 

 Soc. Nat. Hist., voL 7, 1884, p. 38. — Hall and Simpson, Nat. Hist. New York, 

 PaL, voL 6, 1887, p. xix.— Miller, North Amer. Geol. and Pal., 1889, p. 298.— 

 Ulrich, GeoL Surv. Illinois, vol. 8, 1890, pp. 385, 496. — Simpson, Fourteenth 

 Ann. Rep. State Geol. New York for the year 1894, 1897, p. 537.— Nickles 

 and Bassler, Bull. 173, U. S. Geol Surv., 1900, p. 50. 



Cosdnium Eichwald (part), Lethaea Rossica, vol. 1, 1860, p. 397. 



Cosdnotrypa Hall and Simpson, Nat. Hist. New York, Pal., vol. 6, 1887, p. xix. — 

 Miller, North Amer. Geol. and Pal., 1889, p. 298. — Simpson, Fourteenth 

 Ann. Rep. State Geol. New York for the year 1894, 1897, p. 537. 



Species of Ooscinium differ from other genera of the family notably 

 in having a cribrose zoarium. This, in connection with the bifoUate 

 growth, round zooecia with conspicuous lunaria and soHd interspaces, 

 makes the recognition of the genus easy. Five or six species are 

 known from Devonian and Carboniferous rocks. 



Genotype. — Ooscinium cyclops KeyserHng, Carboniferous of Russia. 



