BEYOZOA. 183 



Stlctoporella.] 







The broad, maculose zoaria of S. frondifera are not likely to be confounded, although 

 the two species are undoubtedly closely related. The following variety is good evi- 

 dence of that. 



Formation and locality Not uncommon in the lower third of the Trenton shales, at Minneapols, St. 

 Paul, and several localities in Goodhue and Filmore counties, Minnesota. 



Mus. Reg. Nos. 5943. 7617. 



STICTOPORELLA ANGULARIS, var. INTERMEDIA n. var. 



PLATE XI, FIGS. 4, 5 and 7. 



This name is proposed provisionally for a form that is common at several locali- 

 ties in Filmore county, but rare in the more northern exposures of the same beds. 

 It differs from typical S. angularis, with which it is often associated, in forming wide, 

 irregular branches, the growth and size being in many instances precisely as in the 

 branching form of S. frondifera. At intervals the surface presents clusters of zocecia 

 with thinner walls and larger apertures than usual. The mesopores are very few, in 

 most cases restricted to the center of the clusters mentioned. Here they may form 

 aggregations, but these are never, as far as observed, so extensive as in S. frondifera 

 One or two rows of them are also commonly present at the rounded margins of the 

 branches. 



In having very few mesopores the variety agrees with S. angularis, while in its 

 wide branches and general aspect it is like S. frondifera. The name intermedia 

 alludes to its position between those species. 



Formation and locality. Rare near the base of the Trenton shales, at Minneapolis, but common In 

 the same beds near Fountain, Lanesboro and Preston, all localities in Minnesota; also at Decorah, Iowa 



Mus. Reg. Nos. 7597, 75P9, 7984. 



STICTOPORELLA FRONDIFERA Ulrich. 



PLATE XI, FIGS. 12-19. 



Stictoporella frondifera ULKICH, 1886. Fourteenth Ann. Kept. Geol. Nat. Hist. Surv. Minn., p. 72. 



Zoarium consisting of broad, irregularly branching, flabellate or undulate expan- 

 sions, 1 or 2 mm. in thickness, the whole attaining a hight of from 50 to 100 mm. 

 Edges rounded, with small pits (mesopores) in two or more rows. Surface with con- 

 spicuous macula; consisting of greater or lesser aggregations of mesopores, sometimes 

 a hundred and more, generally about fifty or less. These maculae are from 3 to 5 mm. 

 apart, sometimes arranged in rows, but oftener their distribution is decidedly irregular. 

 Between them the surface is occupied by the rounded zooecial apertures and meso- 

 pores, the latter small and unequally distributed, varying in number from one, two, 

 or even three to each of the former. Walls ridge-shaped, thick, usually nearly 



