ODONTOPTERIS GENUINA IN RHODE ISLAND 
Eva M. Rounp 
(WITH FIVE FIGURES) 
One of the most characteristic and common fossils of Rhode 
Island is Odontopteris genuina Grand’Eury. These plants appar- 
ently grew to great size around the coal swamps of the Narra- 
gansett Basin during the Carboniferous, somewhat like the tree 
ferns of the tropical forests of the present day (fig. 1). The 
fronds appear to have been bifurcate, the angle formed by the 
branches being about 90° (fig. 2). The rachis is striated and 
clothed with short pinnae, the latter having enlarged pinnules at 
their tips and being more separated than those of the expanded 
parts of the frond. The pinnae vary considerably, sometimes being 
short or at other times attaining a length of over 15cm. The 
pinnules often vary in shape on the same specimen, some being 
falcate and acute, while others are oval and rounded at their 
apices. The acute type of O. genuina is very common in the state, 
and may have come about as a result of the conditions under which 
the fossils were originally imbedded. The pinnules appear to have 
been firm in texture and convex or “bombe”’ in shape. If these 
shapes were squarely imbedded they would appear oval (fig. 3a) 
when fossilized, while more pointed effects would result from pres- 
ervation at a slight angle (fig. 3b; fig. 4a, b), and long, narrow 
effects from still greater angles (fig. 5a). While these forms have 
pinnules 3-8mm. broad by 10-16 mm. long, the illustrations 
from Pawtucket show much larger sizes and resemble those figured 
by ZEILLER' from Commentry, France. The Pawtucket specimens 
do not appear to have been as firm and thick as the smaller Rhode 
Island types, and the borders are inclined to be less even. The 
pinnules also were evidently flat rather than convex in shape and 
somewhat cyclopterid in appearance (fig. 3c, d; fig. 56). 
* ZEILLER, C. R., Etudes sur le Terrain Houiller de Commentry. #/. 24. 1888. 
397] [Botanical Gazette, vol. 72 
