BRYOZOA. : 305 
Monotrypa intabulata.] 
MonoTRYPA INTABULATA, N. Sp. 
Compare Monotrypa rectimuralis ULKICH, 1890, Geol. Sur. Ill., vol. viii, p. 462. 
Fic. 20. Monotrypa intabulata, n. sp. Upper half of Galena shales, Goodhue and Fillmore counties, 
Minnesota. Collection of E. O. Ulrich. a, transverse section, x18, showing subequal size of tubes, their 
thin walls, and the lucid spot.in the angles of junction; b, vertical section, x18, the tubes filled chiefiy 
with clayey matrix; c, transverse section, x18, of a variety from Fountain, Minnesota, provisionally 
referred to this species. It has larger zocecia than usual, while the size of the latter seems also to be 
rather less equal. 
Zoarium forming subhemispherical or depressed-spherical masses, generally 
between 30 and 60mm. in diameter and 15 to 30 mm. in hight; lower surface 
usually less convex than the upper and sometimes partly covered by an epitheca. 
Celluliferous surface even, covered with subequal, thin walled, polygonal zocecial 
apertures, of which the usual number in 3 mm. is between eight and nine. In sey- 
eral small examples found near Fountain, the number is between seven and eight. 
Conspicuous and regularly arranged clusters of large cells are wanting, though here 
and there one or several zocecia may be of unusual dimensions. 
Internal characters: In transverse sections the walls are exceedingly thin, but 
where well preserved their duplex character is determined by minute triangular, 
seemingly open spaces at the angles of junction, formed by the separation of the 
walls of adjoining tubes.> Here and there a young zoccium is met with, but true 
mesopores and acanthopores as well, are unquestionably wanting. In vertical sec- 
tions the walls form nearly straight lines (merely curving to adapt themselves to the 
growth of the zoarium) being entirely without the crenulations so characteristic of 
the typical species of the genus. Diaphragms also seem to be wanting, and most of 
the tubes of specimens from shaly strata are in great part filled with the matrix. 
At first I believed this species must be the same as the M. rectimuralis Ulrich, 
the types of which were collected from nearly equivalent beds in southern Illinois. 
The absence of diaphragms was explained by the supposition that they had been 
-20 
