52 
Locality and Horizon. In the top of the lowest Trenton 
beds exposed at the Stewart quarry, Rockland, and at an expo- 
sure of the same horizon about 3 miles east of Ottawa. 
Rafinesquina? , sp. undt. 
Plate III, figures 10, 11 
In the upper beds at Rockland and less frequently at Ottawa 
is found a Rafinssquina-like brdchiopod. Only the pedicle valve 
is present and no specimen is sufficiently well preserved to admit 
of an adequate description. In general size and shape it resem- 
bles Rafinesquina alternata , but numerous exfoliated specimens 
show a long, medium septum with a shorter one on each side. 
Along the hinge line are small but evident crenulations and the 
whole surface is highly punctate. One specimen was found in 
the top of the Leray beds at MacLaren landing. In spite of the 
weathering of the specimens the three septa are well defined. 
Formation and Horizon. In the lowest Trenton at Rockland 
and Ottawa &nd in the uppermost Black River at MacLaren 
landing. 
Cyrtodontaf planumbona n. sp. 
Plate IV, figures 1, 2 
The measurements of the best-preserved specimen are: 
length 28 mm.; height 16 mm.; depth of convexity 5 mm. 
Shell evenly convex, umbonal ridge not distinct, beak in anterior 
quarter of shell. Posterior margin evenly-rounded with a rather 
narrow curve, ventral margin gently convex, anterior marginal 
curve narrower than that of the posterior. The interior mould 
— the only specimen at all well preserved — shows three con- 
centric growth ridges, broad, and so rounded as to be hardly 
perce'ptible. Across the umbonal region are faint traces of 
three radiating striae, far apart and indistinct. The anterior 
muscle scar is fairly prominent, the posterior is larger and but 
very faintly impressed. The pallial line is present, though 
indistinct. 
It differs from Cyrtodonta scala and C. solitaria in size and 
general shape, from C. lamellosa in outline, particularly the 
form of the anterior and posterior margins. 
