NORTH AMERICAN EARLY TERTIARY BRYOZOA. 205 



The cryptocyst is partially calcified. It bears laterally two opcsiular indenta- 

 tions serving for the passage of the parietal muscles. Between them a semitubular 

 projection forms the polypidian convexity protecting the tentacular sheath of the 

 polypide. This convexity is an incomplete polypide tube which is found more 

 perfected in the Thalamoporellidae and Steganoporellidae. 



The onychocellarium which is always interzooecial. is a modified zooecium, and 

 is also a complete avicularium. The axis of the mandible has one or two mem- 

 branous expansions. All zooecial modifications cause a corresponding modification 

 of the onychocellarium. Thus, when the retractor muscles of the polypide arc 

 attached in the inferior zooecial angles, the polypidian indentations are unsym- 

 metrical and the onychocellarium also becomes unsymmetrical, having only one mem-' 

 branous expansion. 



The pivot of the onychocellarium is formed by two strong lateral teeth dividing 

 the opesium into two parts. The inferior part serves for the passage of the elevator 

 muscles of the mandible; the superior part serves for the passage of the occlusor 

 muscles of the mandible. 



The operculum is an opercular valve surrounded by an arched, chitinous scler- 

 ite, which may or may not be distinct from the ectocyst. 



The mural rim and the cryptocyst are both derived from the olocyst and formed 

 of elements which group themselves in radiating series around the opesium (fig. 

 56M). The olocyst ceases in the old zooecia which become vacuolar (fig. 56N). 



Genus ONYCHOCELLA Jullien, 1881. 



1881. Ont/cJwcella JULLIEN, Note sur uue nouvelle division cles Bryozoaires Cheilostomieiis, 

 Bulletin Socifte Zoologique France, vol. 6, p. 277. 



The retractor muscles of the polypide are attached in one of the inferior angles 

 of the zooecia. The opesium is irregularly subtrifoliate. The opesiular indenta- 

 tions serve for the passage of the parietal muscles. The onychocellarium is falci- 

 form with a single membranous expansion. A chitinous ring surrounds the end of 

 the peculiar body; fourteen tentacles. 



Genotype. Onychocclla (Membranipora) angulosa Reuss, 1847. Range. 

 Bathonian Recent. 



ONYCHOCELLA ANGULOSA Reuss, 1847. 

 Plate 32, figs. 31, 32. 



1847. Cellcpora angulosa REUSS, Die fossilen Polyparien rles Weiner Tertiarbeckens, 

 Haidinger's Naturwiss. Ablinndlungen, vol. 2, p. 41, pi. 11, fig. 10. 



1851. Scmiescliara pariaicnsis D'ORBIONY, Paleontologie Francaise, Terrains Cretaces, p. 366. 



1869. Membranipora angulosa REUSS, Studien Tertiarschichten Alpen, Denkschriften k. 

 Akademie Wissenschaften, vol. 29, pp. 253, 262, 291, pi. 29, figs. 9-11. 



1871. Mciiibraniimra angulosa MANZONI, Briozoi Pliocenici Italian!, Sitzuugberichte k. 

 Akademie Wissenscbaften, vols. 59 and 60, pi. 2, fig. 10. 



1874. Membranipora angulosa, REUSS, Bryozoen Oesterreich-Ungarischen Miocans, Derik- 



schrift k. Akademie Wisseuscbaften, vol. 33, p. 185, pi. 10, figs. 13, 14. 



1875. Membranipora aiif/ulosa MANZONI; I. Briozoi del Pliocene antico di Castrocaro, p. S, 



pi. 1, fig. 11. 



