PRODUCTUS 133 



1877. Productus Icevicostus ? Hall and Whitfield, U. S. Geol. Expl. 40th 



Par., vol. 4, p. 266, pi. 5, figs. 7-8. 

 1883. Productus ovatus Hall, Rep. N. Y. State Geol. for 1882 pi (18) 



49, fig. 19. 



1891. Productus pileiformis Whitfield, Ann. N. Y. Acad. Sci., vol. 5, 



p. 582, pi. 13, figs. 13-14. 



1892. Productus ovatus Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, pi. 18, 



fig. 19. 



1894. Productus Icevicostus Keyes, Mo. Geol. Surv., vol. 5, p. 41, pi. 38, 

 fig. 1. 



1894. Productus ovatus Keyes, Mo. Geol. Surv., vol. 5, p. 44. 



1895. Productus pileiformis Whitfield, Geol. Surv. Ohio, vol. 7, p. 470, 



pi. 9, figs. 13-14. 



1899. . Productus Icevicosta Girty, Mon. U. S. Geol. Survey, vol. 32, p. 534, 



pi. 69, figs. 9a-c. 



1900. Productus Icevicostus Weller, Trans. St. Louis Acad. Sci., vol. 10, 



p. 71, pi. 1, figs. 1-2. 

 1903. Productus Iwvicostug Girty, Prof. Paper, U. S. Geol. Survey, No. 16, 



p. 284. 

 1909. Productus pileiformis Girty, Bull. U. S. Geol. Survey No. 377, 



p. 26, pi. 2, fig. 7. 

 1911. Productus pileiformis Girty, Bull. U. S. Geol. Survey No. 439, p. 44, 



pi. 4, figs. 1-2. 

 1911. Productus pileiformis Morse, Proc. Ohio State Acad. Sci., vol. 5, p. 



370, figs. 8a-c. 



Description. Shell thin and delicate, variable in size but usually of 

 medium size or larger, longer than wide, the hinge-line shorter than the 

 greatest width, the cardinal extremities angular. The dimensions of a 

 nearly complete pedicle valve are : length from hinge-line to front margin 

 -j-27.5 mm., length from umbonal region to front margin -|-34 mm., great- 

 est width 27 mm., length of hinge-line 23.5 mm., convexity 22.5 mm. 



Pedicle valve gibbous, the greatest convexity posterior to the middle, 

 the umbonal region prominent and strongly protuberant beyond the 

 hinge-line, the surface arched from the umbonal region to the front with 

 the posterior curvature shorter and somewhat more abrupt, the lateral 

 slopes curving abruptly from the median portion of the valve to the lat- 

 eral margins, and deflected as they approach the cardinal extremities to 

 form rather small auriculations ; mesial sinus entirely absent; the beak 

 small, pointed, and closely incurved. Surface marked by fine, rounded, 

 radiating, more or less flexuous costae, on the posterior portion of the 

 valve they are more regular and increase frequently by intercalation, the 

 intercalated costge increasing in size very gradually, anteriorly the inter- 

 calated costas becomes less frequent, the costae often become more irregu- 

 lar in growth and more flexuous upon the more mature portion of the 

 valve where from two to three costae usually occupy the space of one 

 millimeter; towards the cardinal extremities and extending up on the 

 lateral slopes there are strong and distinct, rounded, transverse 'wrinkle- 



