NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
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Fig. 71. — Family Steganoporellidae Levinsen, 1909. 
A-H. Steganoporella magnilabris Busk 1852. A. View, showing the a and B zooecia, X 20. 
B. C. Operculum of B zooeeium ; X 40 and X 50. D, E. Opercula of a zooecia ; X 40. F. 
Operculum of a zooecia; X 50. G. Section cut through an operculum showing a membrane (m) 
between the main sclerites, X 50. H. Operculum, X 85. Decalcified distal end seen from in- 
side with the basal wall removed. The tentacular sheath (ts) is held by four bands (&) at- 
tached to the distal wall; also there are muscles (Ism) from the distal end of the tentacular 
sheath to the wall (a) which divides the zooeeium. The large retractor muscles (r) are seen 
attached to a tendon, while below there is a smaller pair of muscles ( d ) not attached direct to 
the operculum, but to the frontal wall cpiite close to the operculum. 
I. Back of zooeeium. 
J. View, X 50, showing the tentacular parts attached to the side wall of the proximal corner, 
while the stomach, etc., is in the other corner connected by a long, narrow esophageal tube. 
(A. B, D, E, I after Harmer, 1900; C, F. IT, J after Waters, 1915.) 
K-M. Steganoporella alveolata Harmer. 1900. K. B operculum with its occlusor muscles, 
seen from the inner side, and somewhat distally so as to be considerably foreshortened; cond, 
condyles, united to the basal selerite (bs) of the operculum by the strong ligaments lig ; occl, 
proximal occlusor muscle, the tendon (lend) of which is inserted into the occlusor tubercle 
{occl, t.) of the operculum and gives off a fascia (f) which connects it with the projecting proxi- 
mal end of the main selerite (ms) ; occl' distal occlusor, inserted into the fascia x, line along 
which the operculum passes into the roof of the vestibule. 
L. Basal view of a B zooeeium (basal wall removed). The cryptocyst (crypt) is seen from 
its basal surface; part of the floor of the lateral recesses (Ir) is broken away. Between the 
two recesses is the passage (tube) by which the tentacle sheath passes to the orifice; occl', distal 
occlusors, with their transverse facia (/') ; occl, proximal occlusor with its tendon (tend) ; deyr, 
depressor muscles of frontal membrane ; div, divaricator muscles of operculum ; ms, main selerite 
of operculum. The movements of the tentacle sheath are restrained by four delicate muscles, two 
of which originate from the wall of the tube. 
M. Frontal view of a B zooeeium; occl. t., occlusor tubercle; lig, hinge-ligaments, connecting 
the condyles (cond) with the ends of the basal selerite (bs) ; fm, frontal membrane, into which 
the depressor muscles (depr) are inserted ; mpr, median process, arising from the roof of the tube; 
other letters as in fig. O. (K-M after Harmer, 1902.) 
N. Steganoporella lateralis MacGillivray, 1S95. Back of zooeeium. 
O. Steganoporella neozolanica Busk, 1861. Typical form. Part of transverse section of the 
colony seen from the distal side; b, basal wall; h, vertical proximal wall of one of the lateral 
recesses; mp, distal wall of the flask-shaped cavity of the median process; t, opening into the 
subopercular cavity of the zooeeium. 
P. Steganoporella buskii Harmer, 1900. Proximal wall of a zooeeium showing the insertion 
of the cryptocyst and the two fragmented septulae. (N-P after Harmer, 1900.) 
