188 



BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



The distribution of the diaphragms and cystiphragms is sufficiently 

 illustrated in the accompanying figures. 



Fig. 99. — HoMOTBiTA subramosa. o, fragment of a zoarium, natural size; 6, sxirface of an ordinary 



FRAGMENT, X9, SHOWING THE CYSTIPHRAGMS IN THE ZOCECIAL APERTURES; C, A TANGENTIAL SECTION, Xl8, 

 "WITH ACANTHOPORES "VTOLL DEVELOPED; d, TANGENTIAL SECTION, Xl8, "WITH ACANTHOPORES LESS CONSPICU- 

 OUS; e, "VnERTICAL SECTION OF A TYPICAL EXAMPLE, X18. PHYLLOPOEINA BED OF BLACK RiVEE (DECORAH) 



SHALES, St. Paul, and near Cannon Falls, Minnesota. (After Ulrich.) 



The Kuckers examples differ from the typical H. subramosa in 

 that the zoarium is somewhat smaller, the walls are thinner, the 



Fig. 100.— Homotrypa subramosa. a, tangentla.l section of a Russian specimen, X20; B, several 

 zocecia of the same, X60; c, t"wo portions of a "VERTICAL section, prepared from a young example, 



SH0"WING THE IMMATURE AND MATURE REGIONS, X20. KUCKERS SHALE (C2), ReVAL, EsTHONIA. 



aeanthopores less numerous and smaller, and lastly the clusters 

 of larger cells are more conspicuous. All of these same differences 

 pertain to the early -Trenton form which Ulrich named H. insigniss, 



