Bi, PALEONTOLOGY OF THE EUREKA DISTRICT. 
served in P. (P.) Shumardianus, and, as it occurs in Nevada, it is very 
distinct from the young shells of the latter species. It approaches much 
more nearly P. (P.) navicella, with which it is associated, differing from that 
very decidedly in its truncated apex, much less arcuate ventral valve, and 
broader, less elongate outline. With Productus Murchisonianus it appears 
to present but very few characters in common. 
Formation and localities—Lower horizon of the Devonian limestone, 
south ridge of Atrypa Peak, and west slope of County Peak, Eureka Dis- 
trict, Nevada. 
Productus (Productella) lachrymosus var. limus Conrad (Sp.). 
Plate xiii, figs. 18, 18a. 
Strophomena lima Conrad, 1842. Jour. Acad. Nat. Sci. Philad., vol. viii, p. 256. 
Productella lachrymosa var. lima Hall, 1867. Pal. N. Y., vol. iv, p. 174, pl. xxv, figs. 
29-32. 
This variety of P.(P.) lachrymosus is well represented by specimens from 
the summit of the Devonian limestone at The Gate, where it is associated 
with P. (P.) subaculeatus and P. (P.) lachrymosus var. stigmatus. The median 
depression of the ventral valve and the characters of the spiniferous tuber- 
cles are distinctly marked, as also the general form and size of the shell. 
Formation and locality—Devonian limestone, at The Gate, northwest of 
Eureka, Nevada. 
Productus (Productella) lachrymosus, var. stigmatus Hall. 
Productella lachrymosa var. stigmata Hall, 1867. Pal. N. Y., vol. iv, p. 174, pl. xxv, 
figs. 33-41. 
Compare Productus? Meek, 1868. Trans. Chicago Acad. Sci., p. 92, pl. xiii, fig. 5. 
This strongly marked variety is represented by a fine series of speci- 
mens that present it as found in the Chemung Group of New York and also 
pass towards a more costate variety that, in this respect, draws near the true 
species P. (P.) lachrymosus, but in size and general appearance it is more 
nearly related to the var. stigmatus. The coste or plications are not formed 
by the elongation of the spine bases but by the plication of the shell, and 
