196 Trans. Acad. Sci. of St. Louis. 



in excess of the length as seen in figure 9 of plate XIX, and 

 having the pedicle valve less concave. Several individuals of 

 this form in the University of Michigan collection, the one 

 here illustrated being among them, have been labeled 

 Streplorhynchus inaequalis by Winchell, but they do not wholly 

 agree with authentic specimens of Orthothetes inaequalis 

 which is typically from the upper yellow sandstone bed be- 

 neath the oolite. The type specimens of O. inflatus are 

 three in number, and one of them is the brachial valve of 

 an individual of this broad form, so it seems that White and 

 Whitfield considered both forms as variations of a single 

 species, and it is not improbable that they were co" rect in 

 this supposition. 



Productus punctatus Martin. 



PI. XIX. f. 8. 



Typical examples of this well-known carboniferous species 

 occur in the fauna. All the specimens which have been 

 observed are internal casts of the pedicle valve, the speci- 

 men illustrated being the largest and most perfect example 

 seen. 



SCHIZOPHORIA SUBELLIPTICA ( W. & W.). 

 PI. XIX. f. 6-7. 



The types of this species are from both the magnesian 

 limestone bed and from the subjacent oolite bed although 

 the original description of the species was probably taken pri- 

 marily from the oolite specimens. One well preserved bra- 

 chial valve from the magnesian limestone is much larger than 

 any of the oolite specimens but seems to agree with them in 

 all its essential characters. 



Camarophoria caput-testudinis (White). 



PI. XIX. f. 1-4. 



Original description. " Shell large, subtriangular, sub- 

 cuneate, front rather fully rounded, meeting the lateral slopes 

 at an obtuse angle ; sides somewhat concave, free from plica- 

 tions near the beaks, and sloping to them with gentle incurva- 

 tures, giving the shell an angular appearance about the beaks, 

 which are small, and at which the sides meet at an acute 



