274 THE PALEONTOLOGY OF MINNESOTA. 
(Dekayia. 
Genus DEKAYIA Edwards and Haime. 
Dekayia, EDWARDS and HAtms, 1851, Mon. Pol. Foss. Terr. Pal., p. 277; NICHOLSON, 1879, Pal. 
Tab. Corals, p. 291; 1881, ‘‘Genus Monticulipora,” p. 98; ULRICH, 
1882, Jour. Cin. Soc. Nat. Hist. vol. v, p. 155, and vol. vi, p. 148; also 
1890, Geol. Sur. I1l., vol. viii, pp. 871 and 415. 
Zoaria irregularly ramose; branches subcylindrical or compressed, growing 
from a broad base. Zocecia polygonal, walls thin. Mesopores wanting or very few, 
when present restricted to the macule. Acanthopores originating in the outer part 
of the axial region, in most cases rather widely separated, often of large size; in 
other cases small, and in one instance equalling the zocecia in number. Diaphragms 
straight, in most.cases remote, sometimes from one-half to one tube diameter dis- 
tant in the peripheral region; wanting usually in the axial region. A thin calca- 
reous pellicle often drawn over the zocecial apertures. 
Type: D. aspera Ed, and H., Hudson River group. 
For remarks see under Dekayella, p. 269. For more detailed observations and 
full descriptions of all the known Lower Silurian species, the reader is referred to 
my “American Paleozoic Bryozoa.”* Beside the following, another as yet unde- 
scribed species of Dekayia, with fewer diaphragms, thinner walls and smaller acan- 
thopores than PD. trentonensis, occurs in Minnesota. It is rather rare, and so far 
known only from the Galena shales of Goodhue county. 
DekayiA TRENTONENSIS Ulrich. 
(Not Figured.) 
Dekayia trentonensis ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. vi, p. 151. 
Zoarium dendroid, branches compressed, dividing frequently and rather irregu- 
larly, 4 to 10 mm. in width. Entire hight of zoarium probably not exceeding 8 or 9 
cm. Surface even, or with: low rounded monticules, 2.5 mm. apart; the latter occu- 
pied by clusters of cells a little larger than those in the intermediate spaces, and 
occasionally have a few mesopores at their summits. Zocecia with comparatively 
thick walls, their apertures subangular, about fourteen in 3 mm. Acanthopores 
rather large, moderately prominent at the surface where six or seven are to be 
counted in 3 mm. 
Internal characters: Yn the axial region of vertical sections the tubes have very 
thin and slightly flexuous walls, and are crossed by diaphragms from two to four 
times their diameter distant from each other. Bending into the peripheral region 
*Jour. Cin, Soe. Nat. Hist., vol. vi, pp. 84 and 148-155. 
