108 MISSISSIPPIAN BRACHIOPODA 



1901. Productus arcuatus "Weller, Trans. St. Louis Acad. Sci, vol 11, 

 p. 160, pi. 14, fig. 23 ; p. 185, pi. 16, fig. 15. 



Description. Shell below medium size, usually longer than wide, the 

 greatest width near the mid-length, the hinge-line shorter than the 

 greatest width, the cardinal extremities angular or sometimes a little 

 rounded. The dimensions of a nearly perfect pedicle valve are: length 

 from hinge-line to front margin 15.5 mm., length from umbonal region 

 to front margin 20.3 mm., greatest width 19 mm., length of hinge-line 

 14 mm., convexity 12.5 mm. 



Pedicle valve gibbous, arched longitudinally with the longer curve on 

 the anterior side, the umbonal region rather broad and strongly pro- 

 tuberant beyond the hinge-line, the mesial portion of the valve rather 

 broadly flattened or very gently convex transversely, the lateral slopes 

 curving abruptly to the lateral and cardinal margins, the auricula- 

 tions at the cardinal extremities small, flattened vertically in mature 

 shells but in young individuals the surface of the auriculations is more 

 nearly horizontal ; mesial sinus obsolete ; beak strongly incurved. Surface 

 of the valve covered by rounded, radiating costae, usually measuring about 

 1 mm. from center to center upon the anterior slope, they increase usually 

 by bifurcation upon the posterior slope of the valve and continue across 

 the anterior slope either without division or rarely dividing, occasionally 

 two cost coalesce towards the margin of the valve; on the posterior 

 slope concentric, wrinkle-like markings are present, best developed to- 

 wards the cardinal margin and becoming fainter across the median por- 

 tion of the valve ; the entire surface covered by fine, concentric lines 

 of growth when the shell is not exfoliated. Spine bases usually not con- 

 spicuous, sparsely scattered over the entire surface but becoming more 

 abundant upon the outer half of the valve. Internal characters not seen. 



Brachial valve not observed. 



Remarks. This species is characterized by its small size, the great con- 

 vexity of the pedicle valve with the nearly vertical lateral slopes, the 

 absence of a mesial sinus, the short hinge-line, and small auriculations 

 whose surface is more nearly vertical than horizontal. In some respects 

 the shell resembles a small example of P. burlingtonensis but it differs 

 from that species in the absence of a median sinus and in the vertical 

 flattening of the auriculations. 



Horizon. Kinderhook. 



PRODUCTUS SEDALIENSIS n. sp. 

 Plate XIV, Figs. 1-7 



1891. Productus llairi Miller, Adv. Sheets 17th Rep. Geol. Surv. Ind., 



p. 79, pi. 13, -fig; 17 (not fig. 16). 



1892. Productus Uairi Miller, 17th Rep. Geol. Surv. Ind., p. 689, pi. 13, 



fig. 17 (not fig. 16). 



