128 PALEONTOLOGY OF THE EUREKA DISTEICT. 



cies occur at the same locality a few feet higher in the strata. Their sur- 

 face, however, is smooth, or shows traces of very fine striae, a feature pro- 

 duced probably by maceration or the smoothing of the shell by attrition 

 during the life of the animal. 



Of the Devonian species of Chonetes from the Devonian of the Missis- 

 sippi Basin or New York, C. coronata Conrad (See Pal. N. Y., vol. iv, p. 133), 

 is most nearly related to this in general form. It differs materially in the 

 coarser surface markings, more oblique cardinal spines, smaller ventral 

 foramen, and greater convexity. 



Formation and locality. Lower horizon of the Devonian limestone, 

 Comrj's Peak, Eureka District, Nevada. 



Genus PKODUCTTJS Sowerby. 

 Submenus PRODUCTELLA Hall, R67. 



Productus (Productella) subaculeatus Murch. 

 Plate vii, fig. 2, pi. xiii, figs. 19, 19 a, 20, 20 a. 



For list of synonyms see Davidson's Monograph of British Devonian Brachiopoda, p. 

 99, and Pal. X. Y., vol. iv, p. 154. 



The figures given by Murchison of the type of this species 10 might have 

 been taken from specimens from the Eureka District, so close is the simi- 

 larity between the forms from the two widely separated localities. There 

 are some slight variations in larger specimens but hardly sufficient to indi- 

 cate a varietal distinction in a species of a genus subject to so many and 

 wide departures from what may be considered the types of some of its most 

 typical species. 



The illustrations given in the fourth volume of the Paleontology of 

 New York, plate xxiii, are of smaller shells than those from Nevada, but ap- 

 pear to be specifically identical with them, while the four referred to this 

 species, with a query, from the Devonian limestone of Nevada (Geol. Expl. 

 Fortieth Parallel, vol. iv, p. 36), are evidently referable to a variety of 

 Hall's P. (P.) Shumardianus. 



Professor Hall identifies P. (P.) subaculeatus in the Upper Helderberg 



10 Bull, de la Soc. Geol. de France, vol. xi, p. 255, pi. ii, figs. 9 a, b, c. 



