PLATE XIV 
Fig. 1. Calymene altirostris (Van Ingen) Foerste. A, cranidium. B, C, lateral 
and upper views of cranidium of chief type. St. Clair Spring, Independence 
county, Arkansas; St. Clair member of Niagaran. Types. Van Ingen collection. 
A, magnified 3 diameters; B, C, 2 diameters. 
Fig. 2. Calymene sp. A, B, C, three pygidia. C, lateral view. St. Clair Spring, 
Independence county, Arkansas; St. Clair member of Niagaran. Van Ingen 
collection. Magnified 3 diameters. 
Fig. 3. Proetus vaningeni Foerste. A, B, C, three cranidia. St. Clair Spring, 
Independence county, Arkansas; St. Clair member of Niagaran. Van Ingen 
collection. Magnified 3 diameters. 
Fig. 4. Cyphaspis spinulocervix (Van Ingen) Foerste. A, B, C, three cranidia. 
B, C, showing the points of attachment of the nuchal spine. St. Clair Spring, 
Independence county, Arkansas; St. Clair member of Niagaran. Van Ingen 
collection. Magnified 3 diameters. 
Fig. 5. Cyphaspis arkansanum (Van Ingen) Foerste. A, B, C, three pygidia, 
with a tendency toward a faint marginal depression. St. Clair Spring, Independ- 
ence county, Arkansas; St. Clair member of Niagaran. Van Ingen collection. 
Magnified 3 diameters. 
Fig. 6. Straparollus pervetustus (Conrad). Viewed slightly obliquely, so as to 
show more of the spire. Lockport, New York; from the Medinan. Original of 
fig. 3a on plate 4 bis. Pal. New York, 1, 1847. Specimen No. 1434-1, American 
Museum of Natural History. 
Fig. 7. Modiolopsis orthonota (Conrad). A, right valve; B, left valve. Origi- 
nals of figures la, lb, Ic, on plate 4 bis. Pal. New York, 1, 1847. A, from Medina, 
New York; B, from Lockport, New York; both from the Medinan. Specimen A, 
No. 1433-1; specimen B, No. 1433-2, in the American Museum of Natural History. 
Fig. 8. Modiolopsis primigenia (Conrad). Left valve, cast of interior, showing 
hinge-tooth. Lockport, New York, in the Medinan. Original of fig. 2a on plate 
4 bis. Pal. New York, 1, 1847. Specimen No. 1432-2, American Museum of Natural 
History. 
Fig. 9. StrophonellamilleriP OQYstQ. Pedicel valve. Jeptha Knob, Kentucky, 
in loose chert from the Laurel formation. 
Fig. 10. Dalmanites sp. Fragment from right side of pygidium; outline of 
pygidium unknown. Centerville, Ohio; from basal Silurian, beneath Brassfield 
limestone. 
Fig. 11. Leptaena center villensis Foerste. A, pedicel valve, interior; B, cast of 
same, to show convexity of valve. Concentric wrinkles are present, as described 
in the text, but do not show in the photograph, since the direction of illumination 
chosen was that which brought out the details of the muscular area, rather than the 
wrinkles. Centerville, Ohio; from the upper part of the Brassfield limestone. 
Fig. 12. Brachyprion sp. Interior of pedicel valve. Centerville, Ohio; from 
basal Silurian, beneath the Brassfield limestone. 
Fig. 13. Schuchertella subplana brevior Foerste. Pedicel valve. Centerville, 
Ohio; from the basal Silurian, beneath the Brassfield limestone. 
Fig. 14. Whitfieldella cf. ovoides Savage. A, lateral view; B, cast of interior 
of pedicel valve. Centerville, Ohio; from the basal Silurian, beneath the Brass- 
field limestone. 
