NORTH AMERICAN EARLY TERTIARY BRYOZOA. V 2()l 



FIG. 71. Family Steganoporellidae Levinsen, 1909. 



A-H. Stcganopon-Ilii iniiiniiliilirix Busk 18. r >2. A. View showing the a and B zooecia, X 20. 

 B, C. Operculimi of B zooecium : X 40 Mini < 50. D. B. Opercula of a zooecia ;' X 40. F. 

 nperculum of a zooecia; X 50. G. Section cut through an operculum showing a membrane ( i > 

 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 (6) at- 

 tached to the distal wall; also there are muscles (tsm) from the distal end of the tentacular 

 sheath to the wall (a) which divides the zooecium. 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 quite close to the operculum. 



I. Back of zooecium. 



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, 

 i A. B. D, E. I after Harmer, 1900; C, F. 11. J after Waters, 1915.) 



K-M. Steganoporella alvcolata Harmer, 1900. K. B operculum with its occlusor muscles, 

 seen from the inner side, and somewhat distally so as to be considerably foreshortened; cored, 

 condyles, united to the basal sclerite (6s) of the operculum by the strong ligaments liy ; occl, 

 proximal occlusor muscle, the tendon (1cnil\ of which is inserted into the occlusor tubercle 

 (orcl, t.\ of the oi>errulum and gives off a fascia (ft which connects it with the projecting proxi- 

 mal end of the main sclerite (ms) ; occl' distal occlusor. inserted into the fascia /', #, line along 

 which the operculum passes into the roof of the vestibule. 



L. Basal view of a B zooecium (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) ; dc/tr, 

 depressor muscles of frontal membrane; <7/r, divaricator muscles of operculum ; ms, main sclerite 

 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 zooecium: occl. 1.. occlusor tubercle: lig, binge-ligaments, connecting 

 the condyles (cond) with the ends of the basal sclerite (6s) ; fm, frontal membrane, into which 

 the depressor muscles (dcpr) 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, 1895. Back of zooecium. 



O. Steganoporella neoxolanica Busk. 1861. Typical form. Part of transverse section of the 

 colony seen from the distal side; 6. basal wall; 7i, 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 zooecium. 



P. Steganoporella buskii Harmer, 1900. Proximal wall of a zooecium showing the insertion 

 of the cryptocyst and the two fragmented septulae. (N-P after Harmer, 1900.) 



