BKYOZOA. 117 



Rhinidictya ] 



STOMATOPORA PROUTANA S. A. Miller. 



PLATE I, FIGS. 8-12. 



Stomatopora proutana S. A. MILLEU, 1882. Jour. Gin. Soc. Nat. Hist., vol. v, p. 39. 

 Ropalonaria pertenuis ULRICH, 1886. Fourteenth Ann. Kept. Geol. Nat. Hist. Sur. Minn., p. 59. 



Zoarium adnate, consisting of frequently branching, uniserially arranged zooecia. 

 Zoo3cia slender, clavate, about 0.04 mm. in diameter at the proximal end, increasing 

 gradually in size to from 0.12 to 0.15 mm. at the rounded anterior end ; each 0.6 to 

 0.8 mm. long, with from eight to ten in 5 mm. Aperture subterminal, small, circular, 

 with a slightly elevated rim-like border ; 0.05 to 0.06 mm. in diameter. 



The above describes the usual form of the species, but fig. 12 represents a 

 variety occurring in the lower layers of the Trenton shales of Minnesota, and in the 

 "Pierce" limestone of Tennessee, having unusually large zoo3cia. In this their 

 length varies from 0.8 to 1.1 mm., while the diameter in the anterior third is gen- 

 erally over 0.2 mm., and sometimes as much as 0.3 mm. 



In my preliminary report on the Minnesota Bryozoa this species was erroneously 

 placed under the ctenostomatous genus Rhopalonnria. At the time I thought it 

 advisable to extend the limits of that genus so as to include these delicate species 

 of Stomatopora. Later studies have fully demonstrated the fallacy of such a view. 



Compared with American species, only S. tenuissima and S. inftata Hall, sp., will be 

 found to exhibit any close relations. In the first the zooecia are more slender and 

 longer ; in the second they are much more inflated. S. elongata Vine, from the 

 Wenlock of England, has slightly shorter zocecia of a form very nearly intermediate 

 between those of S. proutana and S. inflata. 



Formation and locality. This species occurs in the "Pierce" limestone of Tennessee, the Birdseye 

 limestone of central Kentucky, and the Trenton shales of Minnesota at Minneapolis, St. Paul and Cannon 

 Falls ; also at Decorah, Iowa. So far it has not been recognized in the Galena, but it is to be found, rather 

 rarely though, in the Utica horizon at Cincinnati, Ohio, and more abundantly near the tops of the hills at 

 that locality. It occurs also higher in the Hudson River rocks at several localities in Ohio and Indiana, 

 and at Wilmington, Illinois. 



Mus. Reg. Nos. 5926, 8066. 



STOMATOPORA INFLATA Hall. 



PLATE I, FIGS. 13-21. 



Alecto inflata HALL, 1847. Pal. N. Y., vol. i, p. 77. 

 Hippothoa inflata NICHOLSON, 1875. Pal. Ohio, vol. ii, p. 268. 

 Stomatopora inflata VINE, Nov., 1881. Quar. Jour. Geol. Soc. London. 



Zooecia resembling those of Hippothon, short and wide when compared with the 

 preceding species, pyriform, the proximal end contracted and springing from the 

 under side of the anterior end of the cell beneath ; eight or nine in 5 mm. Apertures 



