Fig. 15. Rhijncliotretathebesensis 'FoQvs>iQ. Brachial valve. Centerville/Ohio; 
from the basal Silurian, beneath the Brassfield limestone. 
Fig. 16. Liospira depressum Foerste. A, apical view; B, basal view, showing 
callosity on one side of umbilicus. Centerville, Ohio; from the basal Silurian, 
beneath the Brassfield limestone. 
Fig. 17. Lophospira ehlersi Foerste. A, apical part of specimen; B, same 
specimen enlarged, C, D, entire specimens. Centerville, Ohio; from the basal 
Silurian, beneath the Brassfield limestone. 
Fig. 18. Lophospira {Ruedemannia f) centervillensis Foerste. A, fragment 
showing the typical revolving striae along the lower part of the last volution; B, 
entire specimen, showing general form of shell. Centerville, Ohio; from the 
basal Silurian, beneath the Brassfield limestone. 
Fig. 19. Ctenodonta cf .simulatrix Ulrich. A., left valve; B, right valve; both 
magnified 2.4 diameters. Centerville, Ohio; from the basal Silurian, beneath the 
Brassfield limestone. 
Fig. 20. Bellerophon centervillensis Foerste. A, aperture facing upward, but 
margin brokin off; B, enlarged view of the same. C, aperture facing downward, 
but margin broken off. D, attempt at restoration of the margin, in a lateral view. 
PLATE XV 
Fig. 1. Straparollus paveyi Foerste. A, lateral view; B, apical view; C, umbilical 
view, Hillsboro, Ohio; from the Guelph formation. 
Fig. 2. Spyroceras microtextile Foerste. A, small fragments; B, the same 
enlarged; this fragment shows the vertical and transverse striae described in the 
text, but a greater magnification is needed to show these. C, a longer specimen, 
apparently belonging to the same species. Centerville, Ohio; from the basal 
Silurian, beneath the Brassfield limestone. 
Fig. 3. Loxoceras husseyi Foerste. A, a small fragment showing the vertical 
surface striae; B, enlargement of the same; C, a typical specimen of larger size, 
showing the camerae; D, vertical section, showing two of the segments of the 
siphuncle, and faint traces of two more. Centerville, Ohio ; from the basal Silurian 
beneath the Brassfield limestone. 
Fig. 4. Hor^notoma trilineata var. Foerste. Specimen with a shorter spire 
than usual. Centerville, Ohio; from the basal Silurian, beneath the Brassfield 
limestone. 
Fig. 5. Hormotoma trilineata var. Foerste. Specimen with shorter volutions 
than usual. Centerville, Ohio; from the basal Silurian, beneath the Brassfield 
limestone. 
Fig. 6. Hormotoma trilineata Foerste. A, typical form; B, enlargement of the 
same; C, another specimen. Centerville, Ohio; from the basal Silurian, beneath 
the Brassfield limestone. 
Fig. 7. Hormotoma centervillensis Foerste. A, lateral view; B, enlargement of 
the same. Centerville, Ohio; from the basal Silurian, beneath the Brassfield 
limestone. 
Fig. 8. Lyellia thebesensis Foerste. Jeptha Knob, Kentucky, from loose 
chert referred to the Laurel formation. 
