FOSSILS OF THE DEVONIAN. 133 



present various stages of development, from a simple trace on the front 

 margin to where they pass up over the center. 



The form from the Mackenzie River Basin, illustrated by Mr. Meek and 

 not specifically identified, is very closely related to the semicostate variety, 

 if not identical with it, and it occurs in association with Rhynchondla castanea, 

 a form found with P. (P.) lachrymose var stigmatus, at Rescue Hill. 



Formation and localities. Upper horizon of the Devonian limestone, 

 Rescue Hill, and The Gate, northwest of Eureka, Nevada. 



Productus (Productella) speciosus HalL 

 Plate xiii, fig. 8. 



Productus speciosus Hall, 1857. Tenth Ann. Eep. N. Y. State Cab. Nat. Hist., p. 176. 

 Productella speciosa Hall, 1867. Pal. N. Y., vol. iv, p. 175, pi. xxv, figs. 1-11. 



This beautifully marked species occurs in the same beds with the vari- 

 eties of P. (P.) lackrymosa, but it is so distinctly characterized by a narrow, 

 somewhat attenuate utnbo and the closely arranged smaller and more numer- 

 ous spiniferous tubercles that there is little danger of confounding the two 

 species. Of the identity of the New York Chemung Group specimens and 

 those from the Eureka District there is hardly an opportunity to suggest a 

 point in opposition, as they closely coincide in all their specific characters. 



Formation and localities. Upper horizon of the Devonian limestone, 

 Rescue Hill, and at The Gate, northwest of Eureka, Nevada 



Productua hirsutiforme, n. sp. 

 Plate ii, figs. 10,10 a. 



Shell thin, transversely semicircular; width less than the length, unless 

 distorted by compression ; hinge line equaling or a little less than the width 

 of the shell. 



Ventral valve moderately convex and without median sinus, rather 

 abruptly depressed toward the cardino-la^eral margins, which are flattened 

 and broadly auriculate; beak small, incurved. Dorsal valve concave and 

 following the curvature of the ventral one. 



