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Subcarboniferous Fossils from New Mexico. 307 
number of specimens may be selected from the Upper Silurian rocks, 
in the island of Gottland, in the Baltic sea, and mixed with a like 
number of specimens from the upper part of the Niagara Group, at 
Waldron, Indiana, and it will be found extremely difficult for an ex- 
perienced collector to separate them. 
2. Spirifera rockymontana.—This species is represented by a single, 
small, somewhat distorted specimen, but there is very little doubt 
about the identification. | 
3. Spirifera striata.—This species is found in Bolivia, Ireland, 
England and Europe, as well as other distant localities, but is rare in 
the Mississippi valley and. the Appalachian range, It is an everchang- 
ing species, and yet, throughout all its variations and wide geographi- 
cal distribution, it is known only in the Subcarboniferous. It occurs 
in New Mexico in all its forms, from less than an inch to three 
inches in width, and having a length, in some specimens, equal to 
the width, and in others but little more than half as great. The 
hinge line occurs shorter than, equal to, and longer than the greatest 
width of the valves below. The plications are finer on some speci- 
mens than on others, and increase in number with the growth of the 
shell. Throughout all the changes, the ventral valve distinguishes 
the species by the almost uniform width of the cardinal area, and the 
gradually widening mesial sinus toward the front, with a corresponding 
increase in number of the plications, 
A, Athyris lamellosa.—This species occurs in the Subcarboniferous 
of Europe, and has been found within the Mississippi valley, and at 
other places in the West. 
6. Athyris planosulcata.—This species occurs in the Subcarbonifer- 
ous of Europe, and in the Keokuk Group of Iowa and Illinois. 
6. Orthis resupinata.—This species occurs associated with Spirifera 
striata, at various localities in Europe, but is quite rare in America. 
7. Orthis michelini.—This is another species of world-wide distribu- 
tion and great verticalrange. It occurs in the Burlington, as well asin 
all the other groups of the Subcarboniferous, 
8. Productus semireticulatus.—This species, again, is world-wide in 
its distribution, and is common to the Burlington and Keokuk Groups. 
9. Productus vittatus.—This species was described from the Keokuk 
Group of Iowa. 
10. Rhynchonella pustulosa.—This species was described from the 
Burlington Group of Iowa. 
11. Platyceras wquilaterale (misspelled equilatera).—-This species 
