EARLY TERTIARY CHEILOSTOME BRYOZOA. 39 



sen, in 1909, having proved the identity of the hirvae formed the 

 family of Escliarellidae, but the name is badly chosen, for it is 

 based on an archaic genus which the more recent work will not 

 permit us to employ. 



According to the form of the operculum we may class the 

 numerous genera of this family in the following four large groups : 



Schizoporellae, 

 Hippoporae, 

 Peristomellae, 

 Microporellae. 



Evidently the hydrostatic and reproductive functions are iden- 

 tical in each but they operate in a quite variable manner. These 

 variations added to those of calcification, which is also an important 

 function, permit the establishment of a large number of genera 

 almost all rather natural however, which facilitate the study of this 

 very important family. 



First Group. SCHIZOPORELLAE. 



The operculum is semilunar; the proximal border bears a slit or 

 rimule which opens the compensatrix. The muscular attachments 

 are two small, symmetrical tuberosities more or less removed from 

 the border. When the proximal border of the aperture is linear it 

 serves as a pivot for the operculum ; when it is arched and the rimule 

 very large, the pivot of the operculum is formed by two projecting 

 interior condyles. 



The genera of this group with their geologic range are listed 

 below; those marked with an * are represented in the American 

 Eocene and Oligocene: 



'^Schizopodrella^ new genus. Lutecian-Recent. 



*Stephanosella, new genus. Jacksonian-Recent. 



"^Lacerna Jullien, 1888. Lutecian-Eecent. 



*Buffonella Jullien, 1888. Senonian-Eecent. 



*Arthropomu Levinson, 1909. Jackscnian-Eecent. 



Phonicosia Jullien, 1888. Helvetian-Eecent. 



*/SchizomaveUa, new genus. Jacksonian-Recent. 



*Dakarla Jullien, 1903. Lutecian-Eecent. 



*MetroperieUa, new genus. Jacksonian-Eecent. 



^Emballotheca Levinsen, 1909. Jacksonian-Eecent. 



*Tetraplaria Tenison Wood, 1878. Jacksonian-Eecent. 



Nimha Jullien, 1903. Eecent. 



GemeUipora Smitt, 1872. Miocene-Eecent. 



Characodmna Maplestone, 1900. Miocene. 



