186 



BULLETIlSr 77, UNITED STATES NATIONAL MUSEUM. 



of zooecia larger than usual surrounding a granulose central space 

 made up of mesopores. Zooecia oblique in youthful stages, direct 

 and angular in the more mature condition; about eight in 2 mm. 



b 



Fig. 97.— Homoteypa similis. a, surface of a Minnesota specimen, X18, showing a MAcxn:,A and 



NEIGHBORING ZOCECIA; 6, TWO PORTIONS OF A TANGENTIAL SECTION, X 18, PREPARED FROM AN AUTHENTIC 



Canadian example; c, vertical section, X18, of the same specimen, illustrating the charac- 

 teristic GRADUAL OUTWARD BEND OF THE TUBES AND THE TABULATION. LOWEST BEDS OF THE TRENTON 

 LIMESTONE, OTTAWA, CANADA, AND NEAR TRENTON FALLS, NeW YoRK. (AFTER UlRICH.) 



Acanthopores inconspicuous at the surface; mesopores absent save 

 in the maculae. 



The views presented in tangential sections of both American and 



Fig. 98.— Homoteypa similis. a, fragment of a branched zoarium, natueal size; 6, tangential 

 section, x20, illustrating the structxire corresponding to the upper half of figure 97; 6, c, 

 vertical section of same specimen, x20, showing identity with the internal structuee of 

 American examples. "Wassalem beds (D3), Uxnoem, Esthonia. 



Russian specimens are shown in the accompanying illustrations. 

 The marked peculiarities of the species are best seen in vertical sec- 

 tions where the tubes are noted to bend outward very gradually. 

 In the immature region the diaphragms are but shghtly curved; 



