124 GEOLOGY. 
opposite valve; mesial ridge conspicuous on the anterior prolongation, the whole marked with | 
deep pits, almost as numerous as the spines of the opposite valve; visceral regions of both 
valves have indistinct irregular transverse ruge.’’ 
PRODUCTUS SEMIRETICULATUS. Martin. De Konninck. Monographie, p. 83. 
This widely-distributed species occurs at several points on our route. In the cherty lime- 
stone at Camp 73, near the junction of the Great and Little Colorados, it is found in the 
greatest abundance, associated with Spirigera subtilita, &c. It here attains a large size, fully 
equalling in this respect any specimens of this species which have been figured. In all those 
from this locality the form of the shell is strongly revolute, the striae coarse, and the annular 
folds upon the wings, and over the visceral region very conspicuous. This is the largest and 
most strongly marked variety which I met with, and seems to correspond with Marcou’s figure, 
Geol. N. Amer. Pl. VI, fig. 6. From Pecos village I havea more delicate form, smaller in size, 
with markings all finer than the last. 
The limestone at Camp 73 contains considerable numbers of a smaller Productus, of which 
the form is strongly revolute, the antero-posterior diameter being much less than the transverse; 
the visceral disk reticulated, and the anterior surface marked with beautifully regular and par- 
allel striw, on which are set numerous delicate but long tubular spines. In many respects this 
resembles P. semireticulatus var. sulcatus, but the spines crowning the cost between the wings 
and the umbo of the ventral valve do not exist in my specimens, and the spines of the anterior 
surface are much more conspicuous. It has seemed to me best to consider it a variety of P. 
semireticulatus, but further examination may prove it to be new. 
The same shell has been collected in Kansas by Messrs. Meek and Hayden. 
PRODUCTUS NODOSUS, (n. sp.) 
Plate I, figs. 7, 7d. 
Shell of medium size, strongly revolute; antero-posterior diameter less than its breadth; 
beak pointed, extending slightly beyond the cardinal border ; wings very small, much plaited, 
like the entire surface of the ventral valve, covered with numerous fine, distinct and uniform 
thread-like strie ; ventral valve without sinus, but the mesial line is marked by a row of large 
and remote nodes, which extend from the beak-to the anterior margin, and toward which the 
contiguous striz converge. The strie are scarcely more numerous on the anterior border than 
on the beak ; a few are introduced without bifurcation, but the increased space is covered by 
a gradual calatgemant of the stri# and a widening of the space between them. Visceral 
_ region arched and without reticulation ; entire surface spineless, unless the nodes of the mesial 
linesare the bases of large spines. Barat valve striated like the ventral, often without nodes 
or spines. Antero-posterior diameter 1.08 ; breadth 1.50. 
This beautiful species has some Se AS in form and markings to P. Cora, to P. Alto- 
nensis, N. & P., and to P. Hildrethianus, N. & P., and may be grouped with them; but by the 
entire absence of spines, the parallel and vintform strie, and particularly by the row of nodes 
along the mesial line, it is distinctly separated from all known species. 
Locality and formation.—Limestone of Carboniferous age ; Santa Fé, New Mexico. 
PRODUCTUS SPLENDENS? Norwood & Pratten. Jour. Acad. Sct. Phila., May, 1855, p. 11, 
pl, fg. 6. 
In the limestone of the Coal measures on the Santa Fé road, ten miles west of Burlingame, 
Kanes, I collected specimens of what appears to be this species, though of smaller size, more 
evolute, and less ag striated than that described by Norwood and Pratten. 
