50 BRYOZOAN FAUNA OF THE ROCHESTER SHALE. 
PSEUDOIIORNERA DIFFUSA (Hall). 
I'!. XVIII, figs. 6-9; PI. XXIII, figs. 1-3. 
Retepora diffusa Hall, Nat. Hist. New York. Pal. II, 1852, p. 1G0, pi. 40C. 
Pseudohornera diffusa Roemer, Leth. geog. Leth. Pal., i, Alias, 1876, pi. 12, fig. 2. 
Drymotrypa diffusa Ulrich, Geol. Survey Ellinois, VIII, 1890, p. 399, pi. 53, fig. 7, 7b. 
Drymotrypa diffusa Grabau, Bull. New York state Mus., No 45, L901, p. 109, fig. 09. 
Compare Polypora ? problematic a Vine, Quart. Jour. Geol. Soc. London, XXXVIII, 1882, p. 02. 
This, the genotype, has bee;, fully figured and described by Hall and Ulrich. and the fol- 
lowing description is inserted mainly for the sake of completeness. 
Zoarium, a loosely spreading frond growing in a plane and consisting of branches about 
1./) mm. in diameter, dividing dichotomously at short intervals; an entire zoarium about 
50 mm. in both height and width. Celluliferous side bearing from 4 to 6 rows of zoceciaj 
springing from a thin double lamina. 5 zocecia in 2 mm. measuring lengthwise. Noneellu- 
liferous side marked by 6 to 8 longitudinal stria 1 . 
This beautiful form is readily recognized by its dichotomously dividing, nonanastomosinj 
branches, the longitudinally striated reverse and the smooth, slightly rounded obverse bear- 
ing 4 to <i ranges of zocecia. The associated species, V . niagan nsis, has a similar method of 
growth, but may easily be distinguished by its usually angular obverse, bearing circular 
apertures, and fewer ranges of zocecia. 
The collect kjiis of t he I ". S. Nat ional Museum contain specimens of Polypora? problematicm 
Vine, identified by the author of that species, which are closely related if not identical with 
Hall's species. At any rate, Polypora .' problematica is the European representative of 
Ps( udohoi in /a diffusa. 
Occurrence. — Rather uncommon in the Rochester shale at Lockpori and Rochester, N. Y., 
and at Grimsby, Ontario. 
Catalogue number, 43389, (J. S. National Museum. 
Family PENESTELLID^] Ivin<r. 
Genus FENESTELLA Lonsdale. 
Zoarium flabellate or funnel shaped, celluliferous on the inner side; branches generally 
straight, sometimes flexuous, connected at regular intervals by dissepiments, apertures in 
two lows, separated by a plain or t ubcrculatcd keel. 
FENESTELLA CR1BROSA I hill. 
PI. XIX, fig :: 5. 
Fenestella cribrosa Hall, Nat. I list. New York. Pal. LI, 1852, p. L66, pi. 40D, figs. 3a, 1.. 
Original description. — Frond expanded or cyathiform; branches strong, irregularly bifurcating; sur- 
face striated; transverse liars or dissepiments thin, scarcely enlarging at their junction with the 
branches; fenestrules small, quadrangular, sometimes oval; poriferous side unknown. 
Fenestrules eleven in the space of three lines longitudinally, and eighteen in the same space 1 rans- 
versely. 
This species is readily distinguished by the small angular fenestrules, which are much more numerous 
than in the same space in any other species in this group; the branches are quite as strong, or even 
stronger than in F. elegans. It is easily distinguished, therefore, by the nbncelluliferous side alone. 
The specimen in the collections of the American Museum of Natural History, marked as 
the type of this species, does not agree with either Hall's description or figures, but appears 
to be an example of Polypora incepta. In the Rochester shale at the localities mentioned 
below, several examples of a neat little Fenestella have been found which agree in all essential 
respects with Hall's description and figures. Under these circumstances the writer believes 
that the specimen now designated as the type of the species has been inadvertently marked 
as such, and that the original type, which possibly has been lost, was an example of the form 
figured on PL XIX as F. cribrosa. 
