EARLY TERTIARY CHEILOSTOME BRYOZOA. 41 



METROPERIELLA BIPLANATA, new species. 



Plate 4, fig. 4. 



Description. — The zoarium is free, formed of two flat lamella?, 

 back to back and inseparable. The zooecia are much elongated, dis- 

 tinct, fusiform; the frontal is convex and formed of a tremocyst 

 with numerous very fine pores. The apertura is oval, formed of a 

 semilunar anter and with a wide, rounded rimule, separated by two 

 inner condyles. The ovicell is hyperstomial, large, globular, salient; 

 it completely surrounds the apertura, forming about it a very pro- 

 nounced peristomie, in which is placed its special orifice; the peris- 

 tomice is very irregular. The median avicularium is small, little 

 salient, in the immediate vicinity of the rimule. 



,, . A . fAa— 0.16— 0.18 mm. 



Measurements. — Aperture \ ^ „ . , 



1 m— 0.1-4 mm. 



„ . fZs— 1.00-1.10 mm. 

 Zo«e^i^{?,_0.50-0.G0mm. 

 Occurrence. — Middle Jacksonian (Castle Hayne limestone) : Wil- 

 mington, North Carolina (very common). 

 Type.— C'At. No. 62590, U.S.N.M. 



Second Group. HIPPOPORAE. 



The operculum has a projection on each side for muscular attach- 

 ment ; it is generally thick. The apertura bears two lateral denticles 

 or cardelles serving as a pivot for the operculum. The ovicell is 

 always hyperstomial. 



All of the four genera comprising the Hippoporae are represented 

 by rather nimaerous species in the Early Tertiary of North America. 



Hippoporina Neviani, 1895. Danian-Eecent. 



Ilippomenella, new genus. Lutecian-Recent. 



Hippodiplosella Canu, 1915. Jacksonian-Recent. 



Hippozeugosella.) new genus. Priabonian-Miocene. 



HIPPOMENELLA, new genus. 



{Hippos., horse; mene., moon, referring to the horseshoe form of 

 the apertura and to the areas which decorate the ovicell.) 



The apertura bears two small cardelles placed very low and 

 separating a large porta from a small vanna; it is always semi- 

 elliptical (in the interior). The ovicell, hyperstomial, is deeply 

 imbedded in the distal zooecia; it opens by a large opening above 

 the apertura, but it is never closed by the operculum. The frontal 

 is formed of an olocyst perforated laterally by some areolae and 

 supporting a pleurocyst more or less developed. The ovicell bears 



