PLATE X11I[—Continued. 
IPALZOMANON ROEMERI....--. ---- ---- e222 cone ene mone cnn enn on ne eee wane wenn serene ne 
Fig. 12. View showing the cup-shaped summit and general form. Owing to silicification, 
the details of the structure are destroyed. 
“ORTHIS IMBRESSA. 3. Scce see sae ae cota ee nee niae a eee eee a eeile a seine ie ieee im ala —imietak oat 
Fig. 13. Cast of ventral valve. Natural size. 
*CHONETES MACROSTRIATA <.--. 2.25200 <= 202 poo we nnn = oon ne hen = nn renin ee naan 
Fig. 14. Ventral view and outline of the convexity of an average size specimen. 
14a. Same view of an unusually large specimen from which the striated outer surface 
has been removed, showing the inner punctate surface. 
14b. View of ventral valve of asmall, strongly-marked specimen, to which a cardinal 
spine is attached; 14, 14a, are natural size. 
14c. Enlargement of the strie of fig. 14, to show manner of bifurcation. See plate ii, 
fig. 13. 
«CHONETES FILISTRIATA..---. .---00 e222 2+ eee en nee cee nnn ee eens cece cee nee ne teen ec eeene 
Pig. 15. Ventral view of average size specimen, showing surface strie# and cardinal spines. 
15a. Enlargement of the area of the ventral valve, showing the shape of the foramen. 
PRODUCTUS HALLANUS...-..---- ---- ---- --- 2-3 2-22 oe ne enn eon cen ee nee wane ee wees 
Fig. 17,17a. Dorsal and ventral view of average size specimens. 
PRODUCTUS LACHRYMOSUS, var. LIMUS 
Figs. 18, 18a. Lateral and front view of the ventral valve. 
PRODUCTUS SUBACULEATUS .--------------- Bee ose Donec a cos Hosa necasoopaL caecuaaneddccanes 
Figs. 19,19a. Ventral and cardinal views of a specimen from which the outer shell is par- 
tially exfoliated. 
20,20a. Same view of the type of tbe species copied from plate ii, tome xi, Bull, Soc. 
Geol. de France. The spine bases are stronger than in 19, 19a, but in other speci- 
mens they are much as in figs. 20,20a, See plate vii, fig. 2. 
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