134 
Kirtley F. Mather 
apertures occur in 2 mm. transversely and from twelve to four- 
teen in 5 mm. longitudinally. Measuring diagonally, seven is 
the usual number in 2 mm. Interspaces carinate, as wide as or 
wider than the zooecia apertures, carrying at most of the angles 
of junction a moderately large tubercle. Sloping areas varying 
considerably in form, being sometimes hexagonal and at other 
times pentagonal, lozenge-shaped, or irregularly quadrate.'' 
Remarks, Numerous fragments at hand represent a form 
which seems to be indistinguishable from the species which 
Ulrich has thus described. The stems are, if anything, slightly 
more robust as some of them attain a diameter of 1.7 mm. and 
the vestibules into which the zooecial apertures open may be on 
the average a very little larger than those in the type specimens. 
Longitudinal sections show that diaphragms are present, though 
not in abundance, in the axial or primitive portion of the zooecial 
tubes. 
Horizon and locality. Morrow formation: near Ft. Gibson, 
Oklahoma (Station 301). 
Rhombopora snideri n. sp. 
Plate VI, figures^ 6, 7. 
Description. Zoarium a ramose, cylindrical branch, not divid- 
ing dichotomously but throwing off lateral branches at right 
angles to the main stem which has a diameter of from 1.4 to 
1.6 mm. Interval between branches not known as none of the 
specimens in hand display more than one branch; the longest 
of the fragments is 13 mm. in length. Zooecia arranged fairly 
regularly in vertical, transverse, and diagonally intersecting, 
spiral series ; 6i/^ or 7 apertures occur in a single vertical series 
in the space of 3 mm. ; the alignment of the zooecia not rarely 
disturbed. Apertures sub-circular to broadly elliptical, opening 
into a vestibule which is generally hexagonal but in some in- 
stances rhombic in outline, with angles somewhat rounded. The 
ridges between the vestibules are rounded, rarely sub-angular, 
and ornamented with numerous smxall tubuli scattered irregu- 
larly over the surface or arranged in three fairly distinct rows, 
the median one of which is situated along the crest of the ridge 
and is commonly obliterated by weathering; a single, somewhat 
larger and stronger tubulus is normally situated at the junction 
angles of the walls. 
