292 BULLETIN 11, UNITED STATES NATIONAL MUSEUM. 



HEMIPHRAGMA STJBSPHERICUM, new species. 



Plate 10, fig. 2; text figs. 178, 179. 



Zoarium massive, quite variable in shape, but usually of irregular 

 subspherical masses, several centimeters in diameter. Young 

 examples are often uniformly rounded, but in older examples, where 

 the growth is less regular, the zoarium is somewhat irregular, and 



Fig. 178. — HEMIPHRAGMA SUBSPHERICUM. a AND 6, TWO PORTIONS pF A TANGENTIAL SECTION, X20 AND 

 X8, IN EACH CASE CUTTING A MACULA; C, ZOCECIA OF THE SAME SECTION, X40, XLLUSTEATING THE EX- 

 TREMELY THIN SIMPLE walls; d, VERTICAL SECTION, X8, PASSING THROUGH SEVERAL SUCCESSIVE 

 IMMATURE AND MATURE REGIONS; «, PART OF THE SAME SECTION, X20, SHOWING WALLS AND SEMI- 

 DIAPHRAGMS MORE CLEARLY. WESENBERG LIMESTONE (E), WESENBERG, ESTHONIA. 



may attain a diameter of 5 or 6 cm. The zoarial surface is smooth, 

 but clusters of large zooBcia forming the maculae occur at intervals 

 of 5 mm. and are visible to the unaided eye. Zooecial apertures 

 direct, thin-walled, angular, and in contact, five in 2 mm. Mesopores 

 few, often entirely wanting; acanthopores absent. 



In vertical sections of a large specimen the zoarium is seen to be 

 made of a number of zooecial layers, each of which shows an immature 



