OAEBONIFEROUS PERIOD. HI 



collections, it having been found at almost every locality at which collec- 

 tions were made from strata of the Carboniferous period. ' It occurs at the 

 following, among other localities : — Camp Cottomvood, old Mormon road, 

 Lincoln County ; top of Grass Mountain, Ely range, thirty-five miles north 

 of Pioche ; and at Silver Peak, Nevada : head of Partridge Creek, Yavapai 

 County ; Salt Eiver ; and head of Big Dry Fork, Arizona ; Kanab Canon, 

 Arizona : Rock Canon, Wahsatch range, near Provo ; Lake range, Fairfield 

 road, and first camp south of Saint George, Utah ; near Bear Spring ; Camp 

 Wingate, and in the Zuui Mountains, between Camp Wingate and Nutria 

 Spring, New Mexico. 



Productus semireticulatus Martin, sj?. 

 Plate VIII, fig. 1 a, I, and c. 



Anomites semireticulatus Martin, 1809, Petriflcata Derb., 7. 



Anomites productus Martin, 1809, Petriflcata Derb., 9. 



Productus scotictis Sowerby, 1814, Min. Couch., i, pi. Ixis, f. 3. 



Productus antiquatus Sovrerbj', 1814, Min. Conch., i, 15. 



Producta 3£arti7ii Phillips, 183G, Geology of Yorkshire, ii, 213. 



Producta pugilis Phillips, 1836, Geology of Yorkshire, ii, 215. 



Leptcena antiguata Fischer, 1837, Oryct. du Gouv. de Mosc, pi. xxvi, figs. 4-5. 



Leptwna tuhifer Fischer, 1837, ib., pi. xxvi, f. 1 (not Deshayes). 



Productus Inca D'Orbigny, 1843, Paleont. Voyage dans FAmer. M6rid., viii, 51. 



Producta flexistria McCoy, 1844, Synop. Carb. Fossils of Ireland, 109. 



Productus semireticulatus de Kouinck, 1847, Monog. Gen. Product., pi. viii, f. 1. 



Productus semireticulatus Shumard, 1855, Geological Eeport of Missouri, 210. 



Productus semireticulatus Davidson, 1857, Monograph British Carb. Brach. 



Productus semireticulatus Marcou, 1858, Geology of Xorth America, 4G. 



Productus semireticulatus Hall, 1858, Geology of Iowa, i, pt. 2, 637. 



Productus Calhounianus Swallow, 1858, Trans. Acad. Sci. St. Louis, i, 181, 



? Productus Ivesii Newberry, 1861, Expl. Exp. Col. Eiv., Paleont., 122. 



Productus semireticulatus Meek, 1S72, U. S. Geol. Surv. Nebraska, 160. 



Shell large, very arcuate ; width greater than the length, the latter 

 being measured in a straight line from hinge to front ; length of hinge-line 

 sometimes less and sometimes greater than the greatest width of the shell 

 in front of it ; area of both valves distinct, but, as usual in this genus, very 

 narrow ; ears thin, more or less prominent ; lateral and front borders 

 rounded ; front emarginate. 



Ventral valve very strongly curved ; beak depressed and projecting a 

 little or not at all over the cardinal border ; a broad, shallow, obscurely 



