BRYOZOA. 459 



DIPLOTRYPA? DUBIA Ulrich. 



PI. XXXm, flg. 3-3b. 



Zoarium discoidal. Upper surface with the usual style of cell 

 aperture ; lower surface with an epitheca. Zooecial walls slightly 

 wavy. Zooecia direct, circular, seven or eight in two mm. 

 Mesopores comparatively few, small, situated at the angles be- 

 tween the zocecia. Diaphragms horizontal in the zocecial tubes, 

 their diameter or more apart, closely set in the mesopores. 

 Acanthopores wanting. 



As shown in fig. 3 a, the zocecial walls have a peculiar inter- 

 mittent structure, which seems conclusive evidence of the w T alls 

 having been originally minutely porous. 



The small size and number of the mesopores make it some- 

 what doubtful whether this species is properly referred to 

 Diplotrvpa. This character and the absence of acanthopores 

 distinguish it from other described species of the genus. 



Position and locality: Cincinnati group, Wilmington, 111. 



BATOSTOMA TJlrich, 1882. 



("Amer. Pal. Bry." Jour. Cin. Soc. Nat. Hist., vol. V, p. 154.) 

 (For generic diagnosis see p. 379.) 



Such species of the genus as B. implication Nich., and B. 

 jamesi Nich., are characterized by zooecia with thick ring-like 

 walls, irregularly oval apertures, numerous mesopores and 

 acanthopores. Although a closely allied species, B. variabile 

 Ulr., differs conspicuously from them in having few mesopores, 

 and polygonal zooecia. B. fertile Ulr., a species from the Tren- 

 ton shales of Minnesota, differs in the same way, but goes 

 farther in having acanthopores considerably reduced in size. 

 Two undescribed forms deviate from the typical species in very 

 much the same manner, and in one of them both the mesopores 

 and acanthopores are so much reduced in number that they are 

 practically wanting. Through these species the genus is made 

 to resemble Monotrypella and Amplexopora without, however, 

 there being any very intimate relationship. The true position 

 of the genus is between Diplotrypa and Monotrypa. 



