BATOSTOMELLIDJH. 29 
Occurrence. — Very abundant at Lockport, Rochester,. Middleport, and other New York 
localities; Grimsby, Hamilton, and Thorold, Ontario. Rare in the Osgood beds at Osgood, 
Ind. 
Catalogue number, 35517, U. S. National Museum. 
Genus BYTHOPORA Miller and Dyer. 
The oblique apertures drawn out anteriorly, canaliculate interspaces, and few mesopores 
and acanthopores characterize this genus. 
Bythopora spinulosa (Hall). 
PI. XIII, figs. 6, 7; PL XXIV, figs. 12 13. 
Trematopora spinulosa Hall, Nat. Hist. New Yorx, Pal. 11, 1852, p. 155, pi. 40A, figs, lla-c. 
Bythopora spinulosa Nickles and Bassler. Bull. U S. Geol. Survey No. 173. 1900. p. 180. 
Bythopora spinulosa Grabau, Bull. New York State Mus., No 45, 1901, p. 166, fig. 64. 
This little form is easily recognized by its narrow cylindrical branches 1 to 2 mm. in 
diameter, with surface smooth except that, at intervals of about 0.5 mm., sharp, conical 
projections 0.1 to 0.2 mm. in height are developed. 
Zooecia thin walled in the axial region, proceeding in a gradual curve to the surface, where 
they open obliquely; walls in the peripheral region considerably thickened. Apertures 
long, oval, the posterior end somewhat elevated, 7 or 8 in 2 mm. measuring lengthwise. 
Diaphragms and mesopores not developed. Acanthopores wanting unless the sharp 
projections of the surface are ol the nature of these structures. 
Occurrence. — Common at Lockport, Rochester, Lewiston, and Niagara Falls, N. Y., 
Thorold, Hamilton, and Grimsby, Ontario. 
Catalogue number, 35516, V. S. National Museum 
Genus ERIDOTRYPA Ulrich. 
This long-lived generic type is well represented in the Rochester shah' both in the way of 
species and in the comparative abundance of specimens. The characters of Eridotrypa , as 
based on the genotype E. mutabihs Ulrich, a Middle Ordovician species, are ramose zoaria 
having more or less oblique, thick-walled zooecia with diaphragms most closely set in the 
earlier part ot the short mature region, a variable number of mesopores with numerous dia- 
,; phragms, and few small acanthopores. The Ordovician species usually possess ail of the 
generic characters as given above, but those from later formations sometimes diverge widely 
from the generic definitions. E. striata (Hall) possesses the typical generic characters and 
evidently is a survivor ol the E. mutabilis group of species. E spinos'a, however, differs by 
developing a large number of well-marked acanthopores, while E. nodvlosa and E. sohda vary 
in another direction by having diaphiagms in neither the zooecia nor mesopores, these three 
species in all other respects, however, being true members ol the genus. This same variation 
is exhibited in oilier Silurian and Devonian species of the genus, of which six or seven have 
been described, and several new forms have been found. When the knowledge of the genus 
is more complete, it will probably be tound that, although essentially the same general type 
of structure pertains to all, now and then species are developed with characters indicating 
relations to other genera. The vertical sections of E. nodulosa and Bythopora spinulosa 
(Hall), as figured on Pis XI and XII 1, aie certainly very similar 
Eridotrypa spinosa n. sp. 
PI. XII, figs. 1-3; Pi. XXV, fig. 15. 
This fine species is readily distinguished from the described species of Eridotrypa and 
from the associated solid ramose bryozoa by its large, thick-walled zooecia and very numer- 
ous acanthopores. The zoanum is of ramose, frequently dividing cylindrical branches 
about 3 mm. in thickness. The surface of the branches is smooth, the maculse being so 
inconspicuous as to be detected with difficulty. 
