DESCRIPTION OF THE FOSSILS. 
103 
disposed in fascicles, and in some specimens pretty uniformly of three plications in each; others 
are irregular. The mesial elevation is often marked by two fascicles of three plications each, 
even when the iemaining plications are irregularly disposed. 
A comparison of specimens from different localities shows that the one described by me in 
Captain Stansbury’s report under the name of Sp. triplicatus is identical with specimens from 
New Mexico which correspond with the figures given by Dr. Roemer of Sp. meusebachanus. 
Specimens from a limestone in the coal measures of Greentown, Ohio, are more extended 
laterally, and more nearly semicircular than the southwestern specimens; and they likewise 
present some slight differences in the strength and disposition of the plications, hut are clearly 
identical species. 
Locality .—Occurs abundantly at the Pecos villages near Santa Fe, New Mexico; where it is 
associated with the preceding and following species. 
This species has perhaps a wider geographical distribution than any one of this genus yet 
known upon the continent. Dr. Roemer cites the species from the San Saba valley, Texas, twenty 
miles below the old Spanish forts. It occurs likewise in considerable numbers at Greentown, 
Ohio, where the writer collected it in 1841. It is known in northern Illinois and as far north 
as Nebraska, and there can be little doubt hut it will be found in limestone of the same age in 
the region of the Great Salt Lake. 
PRODUCTUS, Smoerby. PRODUCTUS SEMIRETICULATUS.—Plate II, figs. 16, 17. 
Anomites semireticulatus, Martin, 1809. 
Productus semireticulatus, P. Martini, P. antiquatus, &c., of authors. For synonomy and 
references see De Koninck, Monograph of Productus and Chonetes, page 83. 
Dorsal valve gibbous, subquadrate, beak recurved, umbo prominent; a sinus more or less 
deep extends from near the beak, and becomes deeper and more expanded upon the middle of 
the shell; hinge line equal to the greatest width of the shell; surface marked by longitudinal 
rounded ribs which are more or less regular (often irrregular) in size, increasing in number 
chiefly on the sides of the shell ; these are crossed on the upper half of the shell by concentric 
elevated lines which are nearly of the same size as the longitudinal ribs ; surface tuberculous at 
the decussating of the two sets of lines. 
The specimens in the collection do not preserve the ventral valve, and they are otherwise 
imperfect; but their close resemblance to the figures of De Koninck, as well as identity with 
what are regarded as authentic specimens of this species, leave no hesitation in thus referring 
them. 
The specimens are all strongly marked on the upper half of the shell by decussating lines ; 
and in some the longitudinal ribs exhibit the bases of spines, and in a single specimen the bases 
of spines are preserved at the junction of the ears with the body of the shell. 
This is a very characteristic carboniferous species, being widely distributed both in Europe 
and America. According to Mr. De Yerneuil, this species occurs in the United States at 
Harrisville, Bagdad, and Cuyahoga, Ohio; near Louisville, Kentucky ; near St. Louis, Missouri, 
and at Fort Leavenworth ; in Indiana and Illinois, in Alabama and Tennessee, and at Bloss- 
burgh, Pennsylvania. 
The three first-named localities are in the Chemung group ; and some of the others are in the 
carboniferous limestones below the coal, while others are in the coal measures, or upper car¬ 
boniferous limestone, showing a remarkable vertical range. The specimens under consideration 
are from the coal measures, or upper carboniferous limestone. We know this species also from 
Fort Laramie, and it has been brought in various collections from the extreme western and 
southwestern extension of the carboniferous formation in the United States and Mexico. 
Locality. —From the Pecos villages. 
