90 MISSISSIPPIAN BRACHIOPODA 



dinal extremities ; cardinal area much narrower than that of the opposite 

 valve and sloping anteriorly so as to form a very wide angle with it, each 

 side a little twisted towards the cardinal extremities and sloping gently 

 from the lateral extremities to the center so that the two sides are not in 

 one plane ; the quadri-partate posterior extremity of the cardinal process 

 is distinctly visible at the center of the cardinal area and fills a portion of 

 the delthyrium of the opposite valve. Internally the cardinal process is 

 prominent and the muscular scars are large and well defined, the inner 

 surface, including a portion of the surface of the muscular scars, is cov- 

 ered with papillse which are arranged more or less definitely in radiating 

 rows towards the lateral and anterior margins. 



Surface of both valves marked by fine radiating costae, variable in 

 width, from 5 to 9 occupying the space of one millimeter, they increase by 

 bifurcation upon the pedicle valve and by implantation on the brachial; 

 they are crossed by much finer, raised, concentric markings which are ob- 

 solete in the furrows between the costae, giving to the costae a sort of cren- 

 ulated appearance; when partially exfoliated the intercostal furrows ex- 

 hibit a row of fine, regularly arranged pits. 



Remarks. The shell which is here identified as Chonetes shumardatws 

 occurs abundantly in the basal Knobstone shales of Kinderhook age, 

 among the ''Knobs," south of Louisville, Kentucky. This is the typical 

 locality for DeKoninck's species, and although his original description 

 and illustrations do not exactly fit the shells which commonly occur 

 there, the identification is believed to be correct. The greatest discrep- 

 ency between DeKoninck's description and the specimens is in the size of 

 the eostse. DeKoninck's statement that 120 occupy the space of 10 milli- 

 meters would make 12 in one millimeter, which is about twice as many as 

 the average among the specimens examined. The specimens studied, 

 however, exhibit much variation in this character, the most finely marked 

 specimen having 9 eostsa in 1 millimeter. DeKoninck's description also 

 indicates a less convex shell than is usual among our specimens. It is a 

 notable fact that among the specimens studied the lesser convexity, finer 

 costae, and greater proportional breadth, are characters which are asso- 

 ciated, and the writer has sometimes been tempted to refer these alone to 

 DeKoninck's species, and to erect a new species for the narrower, more 

 convex, and more coarsely marked forms which are always by far the 

 most numerous. This procedure has not been followed, however, because 

 both types occur together with intermediate forms, and other characters 

 remain much more constant. The row of minute pits in the intercostal 

 furrows of slightly exfoliated specimens is a conspicuous feature of all 

 the shells, and one which is mentioned and illustrated by DeKoninck. 

 Without access to DeKoninck's type specimens, which are not in America, 

 it is not possible to be absolutely certain what shell he had, or to deter- 



