Bkede.] Carboniferous Invertebrates. 83 



spinous projections ; the remainder of the surface of the valve 

 is smooth. Length, 11 mm. ; width, 16 mm. ; convexity, 10 mm. 



Range and distribution : Upper Coal Measures ; Kansas City 

 and Turner, Wyandotte county, Eudora, Lawrence, Lecorop- 

 ton, Topeka, Wabaunsee county. Common or abundant 

 throughout the Coal Measures of the state. 



This species is easily distinguished from the preceding by its 

 smaller size, fainter surface markings, longer hinge, and in the 

 shell being more transverse in appearance, as well as having no 

 fold separating the ears from the umbo. There is also great 

 difference in the internal markings of the two, as can be seen 

 by referring to the plate. 



This species is quite variable in the distinctness of its mark- 

 ings, spines, distinctness of the mesial sinus, and size. The 

 internal markings vary greatly with age, the very old speci- 

 mens presenting the marginal ridge surrounding the visceral 

 and brachial areas, which forms the generic characters of Mar- 

 </<'iu'fcra: but I am inclined ta think that characters that are 

 only developed in aged specimens are not of generic value in 

 the brachiopods. 



Productus pertenttis. Plate IX, figs. 5-5c. 



Productus cancrini Geinitz, Carb. u. Dyas in Neb., p. 54, tab. iv, ff. 6 



a-d, (1866). 

 Productus perienuis Meek, Fin. Rep. U. S. Geol. Surv. Neb., p. 164, pi. 



i, ff. 11a -c, pi. vni, ff. 9a-d, (1872): Drake, Proc. Am. Phil. Soc, 



xxxvi, p. 105, pi. ix, ff. 8-10, ( 1898). 



Meek's description: "Shell small, very thin, truncato-hem- 

 ispherical ; sides and front regularly rounded ; hinge line 

 usually less than the greatest breadth of the valves. Ventral 

 valve without any traces of a mesial sinus, moderately gibbous, 

 the greatest convexity being slightly behind the middle, from 

 which point it rounds off in all directions, but most abruptly 

 toward the beak and ears, which latter are flattened and sub- 

 rectangular ; beak small, slightly prominent, and but little in- 

 curved beyond the hinge line; surface with fine, regular, 

 radiating striae, crossed by small, rather distinct and regular, 

 concentric wrinkles, which latter are generally most strongly 



