308 THE PALEONTOLOGY OF MINNESOTA. 
[Trematoporide. 
The external form, though smaller, is much the same as in M. intabulata 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.—Upper part of the Galena shales (Fusispira beds) at various localities in 
Goodhue county, Minnesota. Also in the Trenton limestone of Canada. 
Mus. Reg. Nos. 7629, 7635, 8026. 
Family TREMATOPORIDA, Ulrich. 
For remarks on this family see p. 289. 
Genus TREMATOPORA, Hall. 
Trematopora, HALL, 1852, Pal. N. Y., vol. ii, p. 149; DyBowsk1, 1877, Die Chetetiden, p. 69; 
ULRICH, 1882, Jour. Cin. Soc. Nat. Hist., vol. v, p. 241; 1883, idem.., 
vol. vi, p. 257; HALL, 1887, Pal. N. Y., vol. vi, p. xiv; ULRICH, 1890, 
Geol. Surv. Ill., vol. viii, pp. 378, 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. 
Zoccial 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 zocecium. 
Type: T. tuberculosa Hall, Niagara group. 
The really essential characters of this genus have been most persistently misin- 
interpreted and overlooked. Even now lam 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 7’. 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 7. ? primigenia and allied species, 
these being much more like Leioclema, Bythopora and Batostomella, on the one hand, 
