NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
205 
The cryptocyst is partially calcified. It bears laterally two opesiular 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 are 
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. Onychocella Jullien, Note sur une nouvelle division des Bryozoaires CReilostomiens, 
Bulletin Societe 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. — Onychocella ( Membranipora ) angulosa Reuss, 1847. Range . — 
Bathonian — Recent. 
ONYCHOCELLA ANGULOSA Reuss, 1847. 
Plate 32, figs. 31, 32. 
1847. Cellepora angulosa Reuss, Die fossilen Polyparien des Weiner Tertiarbeckens, 
Haidinger’s Naturwiss. Abliandlungen, vol. 2, p. 41, pi. 11, fig. 10. 
1851. Semieschara parisiensis D’Orbigny, 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. Membranipora angulosa Manzoni, Briozoi Plioceniei Italiani, Sitzungberichte k. 
Akademie Wissenschaften, vols. 59 and 60, pi. 2, fig. 10. 
1874. Membranipora angulosa Reuss, Bryozoen Oesterreich-TJngarischen Miocans, Denk- 
schrift k. Akademie Wissenschaften, vol. 33, p. 185, pi. 10, figs. 13, 14. 
1875. Membranipora angulosa Manzoni, I. Briozoi del Pliocene antico di Castrocaro, p. S, 
pi. 1, fig. 11. 
