EAELY TERTIARY CHEILOSTOME BEYOZOA. 31 



Rhagasostoma Koschinsky, 1885, and Euritina Canu, 1900, are the 

 only two genera of this family represented in the Early Tertiary of 

 North America. 



Genus RHAGASOSTOMA Koschinsky, 1885. 



1885. Rhagasostoma Koschinsky, Ein Beitrag zur Kenntniss der Bryozoeu 

 fauna der alterer Tertiarschicliten Bayerns, Paleontographica, vol. 

 32, p. 29. 



The ovicell is hyperstomial and opens above the opercular valve; 

 it has no lateral expansions (compressed process). The avicularia 

 are interzocecial. 



Genotype. — Rhagasostoma liexagonum Koschinsky, 1885. 



Range. — Lutecian-Miocene. 



Genus EURITINA Canu, 1900. 



1900. Euritina Canu, llevisiou des Bryozoaii'es du Cretace figures par 

 D'Orbigny, Bulletin Societe Geologique France (3), vol. 28, p. 411. 



Ovicell hyperstomial, never closed by the opercular valve; avicu- 

 larium interzooecial ; cryptocyst well developed, with three facets 

 separated by two longitudinal grooves ; no dietellae. 



Genotype. — Euritina {Eschara) eurita D'Orbign}^, 1852. 



Range. — Turonian-Eocene. 



Family STEGANOPORELLIDAE Levinsen, 1909. 



The zocecium is divided into two chambers. The proximal cham- 

 ber contains the polypide and the ovaries; it is terminated by an 

 ascending tube, the polypide tube, in which the tentacles are lodged 

 when the polypide is retracted. The upper chamber contains the 

 parietal and opercular muscles. The retractor muscles of the poly- 

 pide are attached in one of the lower angles of the zocecium which 

 causes the general asymmetry of the zocecium. No ovicells. No 

 avicularia. Generally two forms of zooecia, a and B. The two 

 opesiulae are generally not separated from the aperture of the 

 zocecium. The operculum, which is sometimes bounded by a chitinous 

 sclerite proximally sometimes continued immediately into the frontal 

 membrane, is as a rule very large and then suspended by strong 

 hinge-teeth. 



Genus STEGANOPORELLA Smitt, 1873. 



1873, Steganoporella Smitt, Floridan Bryozoa, Kongl. Svenska Vetens- 

 kaps-Akademiens Handlingar, vol. 11, No. 4, p. 15. 



The whole of the calcified part of the frontal area lying proxi- 

 mally to the aperture is a depressed cryptocyst; the aperture of the 

 zocecium is surrounded distally and laterally by a projecting margin; 



