44 BRYOZOAN FAUNA OF THE ROCHESTER SHALE. 
rounded monticules, 3 to 3.5 mm. apart, measuring from center to center; sometimes, 
however, the maculse are developed as sharp or elongate tubercules. Zooecial apertures 
oval, 6 to 7 in 2 mm. measuring lengthwise, with more or less elevated peristomes, each 
bearing two or three rather large and conspicuous acanthopores. Interzooecial spaces 
solid and somewhat depressed, the mesopores being closed at the surface by a pellicle-like 
covering. Mesopores few to numerous, the zooecia sometimes being in contact but more 
often separated from each other by a distance varying from one-half to their entire diameter 
apart. 
The fully matured region of most specimens is so short that good tangential sections are 
difficult to prepare. A section passing through the zooecia just below the surface shows 
that they are oval and marked by rather thick ring-like walls within which acanthopores 
are developed. The mesopores are angular and thin walled, but often the section passes 
through the covering of the mesopores, in which case the walls are not visible, but the 
interzooecial spaces arc occupied by a fine tissue perforated by more or less numerous 
granular-like structures. In deep tangential sections the difference between zooecia and 
mesopores is so small that they arc distinguished with difficulty, each having thin walls 
and being about equal in size. 
Vertical sections present the following characters: In the axial region the zooecia are 
large with very thin walls and no diaphragms. With the inception of the peripheral region 
the walls are slightly thickened, and mesopores and acanthopores are developed, the diam- 
eter of the zocecia beiiiL r lessened by the introduction of the mesopores. The zooecia in 
this region usually show no diaphragms, one or two rarely being developed in each tube, 
but the mesopores exhibit them in comparative abundance. The mesopores also give a 
beaded appearance, being constricted at intervals, diminishing from the interior toward 
the surface and each constriction being marked by a diaphragm. The last diaphragm has 
the minutely perforated laminated tissue developed upon it which closes the mesopores at 
the surface, but other diaphragms in the same tube are often thickened with the same 
tissue, although usually not to the extent obtaining at the surface. 
The solid tuberculated branches with small zocecia surrounded by peristomes bearing 
rather conspicuous acanthopores and with closed interspaces, make Trematopora tuberculosa 
an easily recognized species. The other species of the genus are so different that comparison 
is unnecessary. There is no associated bryozoan with which this species might be con- 
fused, save possibly Eridotrypa n>></u!<>sa, which has a similar growth and strongly tuber- 
culated surface. The zoarium of the latter species, however, is smaller, the zocecia have 
neither peristomes bearing acanthopores surrounding them nor solid interspaces, while 
internally the structure of the two is quite different. 
Occurrence. — Very abundant in the Rochester shale at Lockport, Lewiston, Niagara 
Gorge, and elsewhere in New York and ;it Grimsby and Thorold, Ontario. Rare in the 
Osgood beds at Osgood, Tnd. 
Catalogue numbers, 43618, 35573, 35515, 44427, U. S. National Museum. 
Trematopora whitfieldi Ulrich. 
PI. XXIII, figs. Hi. 17; PL XXVII, Tigs. 16. 17. 
Trematopora whitfieldi Ulrich, .lour. Cincinnati Soe. Nat. Hist., VI. 1883. p. 262. pi. 13, figs. 4 : 4a, 
In the Waldron shales of Indiana may be found numerous specimens of a small ramose 
bryozoan, which has been described by Ulrich under the above name. A few examples 
identical in all respects with the western form occurred in the collections from the Rochester 
shale. Ulrich's original description covers the specific characters fully, and, with slight 
changes, is given below. 
Zoarium slender, ramose, branches smooth, with an average diameter of 2.5 mm., and 
dividing dichotomously at intervals of 10 mm. more or less. True zocecia subequal with 
elliptical apertures, surrounded by thin, more or less distinct peristomes, and uniformly 
arranged in diagonally intersecting series over the entire surface. In these 7 to 8 zooectfi 
