PRODUCTUS 131 



gion to front margin 25 mm. and 25.8 mm., greatest width 30.8 mm. and 

 27.7 mm., length of hinge-line 26 mm. and 26 mm., convexity 10 mm. and 

 9 mm. 



Pedicle valve convex with the greatest depth posterior to the middle, 

 the umbonal region very slightly protuberant beyond the hinge-line, the 

 surface of the valve curving rather abruptly to the cardinal margin, with 

 the curvature only slightly modified towards the cardinal extremities be- 

 cause of the almost obsolete cardinal auriculations, to the lateral and an- 

 terior margins the curvature is more gentle ; mesial sinus entirely want- 

 ing ; the beak very short and obtuse, scarcely differentiated from the um- 

 bonal surface and not extended beyond the cardinal margin. Surface of 

 the valve marked by low, rounded, moderately fine, more or less discon- 

 tinuous, longitudinal costae, and by a few more or less inconspicuous con- 

 centric wrinkles posteriorly, which are strongest towards the cardinal 

 extremities. 



Brachial valve concave, the curvature following that of the pedicle 

 valve with a rather thin visceral cavity, with no mesial fold or sinus. The 

 surface markings entirely similar to those of the opposite valve. 



Remarks. This species is especially characterized by the flattened 

 umbonal region, the almost obsolete beak, and the slight posterior pro- 

 tuberance of the umbo. In its general aspect the form of the pedicle 

 valve suggests an impression of the concave brachial valve of some species 

 of Productus, and for a time the species was so interpreted. A sufficient 

 number of examples having both valves in place have been observed, how- 

 ever, to make it certain that such an interpretation is an incorrect one. 

 and that Winchell was right in his interpretation of the species. The dis- 

 continuity of the radiating markings of the shell, together with the low 

 convexity of the pedicle valve, are somewhat suggestive of the genus 

 Productella, but until the generic characters can be more deefinitely de- 

 termined the species may be allowed to remain in Productus where it was 

 originally placed by Winehell. 



Horizon. Chonopectus sandstone of the Kinderhook. 



PRODUCTUS INDIANENSIS Hall 

 Plate XVIII, Figs. 7-10 ; Plate LXXXIII, Figs. 12-13 



1856. Productus Indianensis Hall, Trans. Albany Inst., vol. 1, p. 47. 



1882. Productus Indianensis Whitfield, Bull. Am. Mus. Nat. Hist., vol. 1, 



p. 47, pi. 6, figs. 6-7. 



1883. Productus Indianensis Hall, 12th Hep. Geol. Surv. Ind., p. 326, 



pi. 29, figs. 6-7. 



1906. Productus indianensis Beede, 30th Ann. Rep. Geol. Surv. Ind., p. 

 1300, pi. 19, figs. 7-7a; pi. 22, figs. 6-7. 



Description. Shell very small, longer than wide, the hinge-line a little 

 shorter than the greatest width, the greatest width near the mi'd-length 



