T. . . „.. , BRYOZOA. 263 



Batostomellldae.l 



Family BATOSTOMELLIDJ], Ulrich. 

 Genus BYTHOPORA, Miller and Dyer. 



Bythopora, Miller and Dybb, 1878, Contri. to Pal., pt, ii, p. 6; Uleich, 1890, Geol. Surv. 111., 



vol. vlil, p. 376. 



Zoaria consisting of very slender branches. ZocBcial apertures very small, 

 oblique, lanceolate, narrowing above. Interspaces variable, generally thick, often 

 channeled. Mesopores and diaphragms very few or wanting. Acanthopores usually 

 present, never numerous, rarely more than one to each zooecium. 



Type : B. fruticosa Miller and Dyer. Cincinnati group. 



The two species found in Minnesota are very similar to the typical species, and, 

 although the latter is not as fully known as we would desire, there can be no reason- 

 able doubt that the three forms are thoroughly congeneric. At least five other 

 species occur in the rocks about Cincinnati, Ohio, but only two of these have been 

 described, both by Nicholson, one as Chcetetes delicatulus, the other as Ptilodictya ? 

 arctipora. Still another form was described by me as B. striata from the upper beds 

 of the Hudson River group at Stony Mountain, Manitoba, and Middletown, Ohio. 



Bythopora hbrricki Ulrich. 



PLATE XXVI, FIGS. 1-6. 



Bythopora herricki Uleich, 1886. Fourteenth Ann. Kep. Geol. Nat. Hist. Surv. Minn., p. 99. 



Zoarium ramose, 20 to 40 mm. high, consisting of slender cylindrical branches, 

 0.8 to 2.0 mm, in diameter, dividing dichotomously at intervals of from 8 to 12 mm. 

 Zooecial apertures small, very oblique, narrow, rounded behind, drawn out in front ; 

 when perfect with a minutely granulose rim, highest posteriorly. Interspaces 

 depressed, wider than the apertures. In the worn condition in which the species is 

 often found, the ramulets appear to be made of thick-walled tubes with oblique 

 apertures. The arrangement of the apertures is in more or less irregular, longitud- 

 inal and diagonal rows, with four in 1 mm. in the latter. Acanthopores small, few, 

 but rarely preserved at the surface. True mesopores wanting. 



Internal characters: A number of thin sections were prepared, but in all the 

 finer details of structure are more or less completely destroyed by crystallization. 

 The sections figured were prepared from an unusually old example. I have endeav- 

 ored to represent the characters shown in these as faithfully as possible, and as I 

 cannot add anything of importance not shown, it is unnecessary to attempt a 

 description of them. 



