180 University Geological Survey of Kansas. 



Productus costatus, (p. 79.) 



8. View of concave side, showing the relation of the two valves. Natural 



size. 



Productus longisplnus, (p. 81.) 



9. Interior of brachial valve of very old specimen. The lateral ridges are 



well developed and extend entirely around the valve, forming a very 



prominent feature. Natural size. 

 96. Brachial valve, showing relation of that valve to the pedicle valve. 



Natural size. 

 9c. Pedicle valve, spines removed. Natural size. 

 9c?. Interior of brachial valve of younger specimen (full grown), showing the 



lateral ridges developed along the hinge only, with slight turn to 



the front where they fade out. Natural size. 

 Hustedia mormon? , (p. 103.) 



10. View of brachial valve. 

 106. Lateral view. 



10c. View of pedicle valve. All natural size. 

 lOd. Surface enlarged to show punctures in shell. 



PLATE X. 



Productus costatus, (p. 79.) 



1. Pedicle valve, showing the ridge between the umbo and the ears on which 



are spines. Natural size. 

 16. Side view of same, 

 lc. Interior of brachial valve, showing adductor markings, cardinal process, 



mesial ridge, lateral ridges, and brachial markings. The border in 



front is matrix between the brachial and pedicle valve. Natural 



size. 



Productus semireticulatus, (p. 78.) 



2. Exterior of brachial valve, showing hinge and beak. Natural size. 



26. Pedicle valve. The umbo of this specimen is narrower than most of 

 the Coal Measures forms, which are probably varietally distinct 

 from the one figured, which is from the Permian, but is figured here 

 on account of its being a much better specimen. Natural size. 



2c. Interior of pedicle valve, showing adductor and diductor markings. The 

 central ones are the adductors. Natural size. 



2d. Interior of brachial valve, showing adductor, brachial and other mark- 

 ings. Natural size. (Small specimen.) 

 Productus punctatus, (p. 87.) 



3. Pedicle valve. Natural size. 



36. Brachial valve, exterior view, showing the beak and hinge. Natural 



size. 

 3c. Lateral view of the same specimen. 

 3d. Pedicle valve of young specimen. Natural size. 

 3c. Cast of interior of the pedicle valve, showing the adductor and diductor 



scars. Natural size. 



