BRYOZOA. 121 



Diastoporina.l 



on the whole, inclined to be irregular, though fairly regular longitudinal series, and 

 sometimes diagonally intersecting rows can generally be made out. The average 

 number in 2 mm. is five or six. 



Compared with B. primitiva Ulrich, from the Hudson River group of Ohio, this 

 species is distinguished by its larger and less tubular zocecia, the interstitial wrinkles, 

 and the non-celluliferous spaces. B. vesiculosa Ulrich, from the Utica shales horizon 

 at Cincinnati, is a nearer relative, but also has smaller zooecia, with the apertures 

 less prominent. In most respects the position of the Minnesota species is inter- 

 mediate between the two Ohio species. 



Formation and locality. Not uncommon in the lower and middle beds of the Trenton shales, at 

 Minneapolis and St. Paul, Minnesota. 



Mus. Reg. No. 5925. 



Genus DIASTOPOR1NA, Ulrich. 



Diastoporina, Ulrich, 1890. Jour. Gin. Soc. Nat. Hist., vol. xii, p. 177. 



Zoarium bifoliate, in general resembling Diastopora (Lamouroux, not Busk). 

 Zooecia subtubular, prostrate, immersed ; apertures constricted, subcircular, not 

 prominent. Interspaces finely punctate and striated longitudinally. 



As only one species is known, it is difficult, if, indeed, it is not impossible in all 

 such cases, to determine the really essential characters of the genus. The striation 

 of the interspaces is a peculiar feature and the chief ground for separating the 

 species from Diastopora, a genus so far not known in strata older than Jurassic. 

 The Minnesota species, however, presents many points of agreement with species of 

 that well known genus, and it may yet be shown that it represents merely an early 

 type of same. This resemblance or possible relationship is paralleled in Mitoclema, 

 Ulrich, and Entalopkora, Lamouroux ; Diplodema, Ulrich and Bidiastopora, d'Orbigny; 

 Protocrisinfi, Ulrich, and Crisina, d'Orbigny; and Scenellpora, Ulrich, and Defmncia, 

 Bronn, and Discocavea, d'Orbigny. In each case the first is founded upon lower 

 paleozoic species, while none of the genera with which they compare are as yet 

 known in rocks earlier than Jurassic. With the exception of Entalophora ( ?Mito 

 clema) one or more species of which occur in the Devonian at the Falls of the Ohio, 

 and in New York (Clonopora, Hall, 1887, Pal. N. Y., vol. vi), none of these cyclostoma- 

 tous genera are known to have had an existence in Devonian and Carboniferous 

 times. Precisely the same is true of Stomatopora, Proboscina, and Berenicea.* But 



Since writing the above, a paper has been received from the Canadian Geological Survey, in which Prof. J.F.Whit- 

 eaves describes one species each of Stomatopora and Proboscina, from the Devonian rocks of the far north. At my request, 

 Prof. Whitoaves kindly sentnie the types of the two species. These were carefully examined by me, with the result, that I 

 still hold that we have no positive evidence of the existence of these genera in Devonian deposits. The first is unquestionably 

 very closely related to Rhopalonarta botellits Vine, and not a Stomotopora. The other may be a Proboscina, but It Is so different 

 from any type of that genus known to me that 1 am obliged to view its relations as highly problematical. 



