88 THE DEVONIAN OF MISSOURI. 



Pentamerella missouriensis n. sp. 

 Plate 24, figures 1-4; plate 23, figure 5. 



Description — General outline of the shell ovate, narrower at the pedicle end, width 

 16 mm., length 16 mm. Pedicle valve moderately convex with the greatest convexity 

 directly above the hingeline. A shallow sinus originates about the middle and occupies 

 a little less than half the width of the shell at the front margin. The back two-fifths 

 of the valve is narrow and projects more than one-third the length of the shell back of 

 the hingeline. The beak is strongly incurved but not over the hingeline. Two faint 

 plications extend back from the margin in the sinus for about one-fourth the length 

 of the shell. Strong plications form the margins of the sinus for about one-fourth the 

 length of the valve. On one side of the sinus there are two strong plications and on the 

 other side three that are not so strong. The plications bounding the sinus are the 

 strongest. The sinus part projects 6 mm., or three-eights the length of the valve in front 

 of the rest of the valve. The hingeline is 6 mm. long, three-eights the width of the shell 



The brachial valve is elliptical in outline. Along the top of the fold it is nearly- 

 straight. The fold originates about the middle of the valve and in a distance of 6 mm. 

 rises to a height of 5 mm. The sides are very abrupt and the top is rounded. Outsjde 

 the fold the valve slopes gently to the margins. The right half of the valve is missing. 

 On the left there is one plication 3 mm. long and another very faint one of about the same 

 length. 



Holotype, one imperfect specimen. 



Snyder Creek shale of Callaway County. 



Pentamerella fultonensis n. sp. 

 Plate 16, figures 21-23; plate 24, figures 10-12 



Description — General outline of the shell subovate, narrower toward the pedicle 

 end, gibbous, width and length subequal. Pedicle valve strongly convex, with the 

 greatest convexity slightly in front of the hingeline. A shallow sinus originates near the 

 middle and occupies more than one-third the width of the shell at the front margin. 

 The beak is strongly incurved but not over the hingeline. A very short median septum 

 is present. The brachial valve is much less convex than the pedicle. The beak projects 

 beyond the hingeline and the greatest convexity is a short distance in front of the hinge- 

 line. A fold that is inconspicuous in some specimens, and strong in others, appears near 

 the front of the valve. Faint indications of rather small plications appear on both 

 valves but are not apparent to the naked eye. The interior of the pedicle valve has a 

 spoon-shaped pit that extends about one-half the length of the shell. In the brachial 

 valv£ the crura are united at their bases, making a V-shaped or U-shaped trough which 

 is attached to the valve at the upper part and extends for about one-half the length of 

 the shell. 



The most striking peculiarity of the shell is the lack of plications visible to the naked 

 eye, and it should, perhaps, be referred to the genus Clorinda. 



Occurrence — Callaway limestone, Callaway County. 



