228 BULLETIN 106, UNITED STATES 'NATIONAL MUSEUM. 



by true perforations called opesiules. The semi-circular aperture has generally 

 a more or less strongly chitinized (or calcareous) , simple operculum, more seldom 

 an opercular valve. Avicularia present. 



Historical. The family Microporidae as delimited by Hincks and by Jullien 

 does not appear very natural because the ovicell system has not been considered; 

 indeed Levinsen in 1909 made some modifications. 



The family may be made more exact by including in it only those genera having 

 an endozooecial ovicell. There is no important difference between the Micro- 

 poridae and the Onychocellidae; the onychocellaria simply disappear or are re- 

 placed by the avicularia. 



As Canu in 1900, 1 has demonstrated, the replacement of the onychocellaria by 

 avicularia is constant in the general line of descent. It is simply adaptation to new 

 conditions of existence. 



In our opinion, the Onychocellidae and Microporidae with the Lunulariidae 

 form one and the same family for which we have adopted Jullien's name Opesiu- 

 lidae, but have retained the first three mentioned as subfamilies. 



Genus ROSSELIANA Jullien, 1888. 

 1SSS. Rosseliana JULLIEN, Mission Scientifique du Cap Horn, Bryozoaires, vol. 6, p. 78. 



The frontal of the zooecium is a cryptocyst of little depth. The opesium is 

 semicircular. The ovicell is endozooecial but prominent. Septulae uniporous. No 

 avicularia. 



Genotype. Rosseliana (Flustra) rosselii Audouin, 1826. 



Canu, in 1900, has badly interpreted Jullien's genus, for the species which he 

 considered as Rosseliana are more often typical Onyckocella. 

 The fossil species are: 



Rosseliana (M embranipora) incompta Reuss, 1874. Miocene. 



Rosseliana (M embranipora) reussiana Manzoni. 1874. Miocene, Pliocene, 



ROSSELIANA PARVIPORA, new species. 



Plate 82, fig. 16. 



Description. The zoarium incrusts bryozoa. The zooecia are elongated, dis- 

 tinct, separated by a deep furrow; the mural rim is thin, salient, complete, and 

 distinct. The cryptocyst is flat, shallow, much larger than the opesium and very 

 finely granulated; the opesium is semilunate, transverse, with a proximal concave 

 border. The ovicell is endozooecial, protruding, and smooth. 



rAo=O.OSmm. . rs=0.34-0.36 mm. 



Measurements. Upesium {, - 1 _ Zooecium 7 



\Z0=0.10mm. [Z2=0.16-0.20 mm. 



Affinities. There is no polypiclian convexity in this species and the opesiular 

 indentations are only visible on rare zooecia. The ovicelled zooecia have a little 

 larger opesium, the breadth of which ranges from 0.12 to 0.14 mm. 



1 Canu, Revision des Bryozoaires du Cr<Stac6 figures par D'Orbigny, Bulletin Soci^te Gdologique 'de France, 

 ser. 9, vol. 28, p. 345. 



