308 THE PALEONTOLOGY OF MINNESOTA. 



ITrem atoporid eb 



The external form, though smaller, is much the same as in M. intahulata and 

 other species of the genus, but the zocecia are larger, and none of them have a wall- 

 structure as described above. 



Formation and locality .—M^-per part of the Galena shales (Fusisplra beds) at various localities in 

 Goodhue county, Minnesota. Also in the Trenton limestone of Canada. 



Mus. Reg. Nos. 7629, 7635, 802D. 



Family TREMATOPORID^, Ulrich. 

 For remarks on this family see p. 289. 



Genus TREMATOPORA, Hall. 



Trematopora, Hall, 1852, Pal. N. Y., vol. ii, p. 149; Dybowski, 1877, Die Chaetetiden, p. 69; 



Ulrich, 1882, Jour. Gin. Soc. Nat. Hist., vol. v, p. 241; 1883, idem., 

 vol. vi, p. 257; Hall, 1887, Pal. N. Y., vol. vi, p. xiv; Ulbich, 1890, 

 Geol. Surv. 111., vol. viii, pp. 373, 418. 



Not Trematopora, Ulrich, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 153. 



Zoaria ramose, branches solid, even or montiferous. Zocecia with oval or sub- 

 circular apertures; surrounded by more or less elevated peristome. Interspaces 

 depressed, sometimes exhibiting the closed mouths of the abundant mesopores. 

 Zooecial tubes with thin walls and few diaphragms. Mesopores irregularly angular, 

 generally exhibiting an obscurely beaded appearance in vertical sections, with a 

 diaphragm at the constriction. Acanthopores superficial, of moderate or small size, 

 one or more to each zooecium. 



Type : T. tuberculosa Hall, Niagara group. 



The really essential characters of this genus have been most persistently misin- 

 interpreted and overlooked. Even now I am not satisfied that they are fully brought 

 out in the above diagnosis, which is practically the same as the one in volume viii of 

 the Illinois reports. The truth is that more study, especially genealogical, is required 

 before it will be possible to delineate even approximately the limits of the genus. 

 Thus, while almost certain that most of the Lower Silurian species placed here by 

 me {e. g. T. primigenia and T. ? nitida) are not really related to T. tuberculosa, I find 

 myself unable as yet to justify their placement elesewhere. 



As stated on a preceding page (289) the type of the genus presents many points 

 of agreement with Batostoma and is probably to be viewed as a later expression of 

 the same type of structure. Not so, however, with T. ? primigenia and allied species, 

 these being much n^ore like Leioclema, B^thopora aqd Batostgrnella, on the one hand, 



