PALEONTOLOGY. 123 
Propuctus CALHOUNIANUS. Swallow. 
This large species was found on no part of our route until we reached the vicinity 
of the Missouri, in Kansas. The specimens there obtained exhibit a striking resem- 
blance, in size and general form, to the most robust individuals of P. semireticulatus procured on 
the banks of the Colorado. The striw are, however, finer, and the tubercles more numerous 
in the Kansas specimens. The fossils presenting these variations from the common form of P. 
semireticulatus might be considered as representing but one of the many phases of this variable 
species, but Prof. Swallow remarks that, in addition to its external character, the markings of 
the interior of the shell of P. Calhownianus are peculiar, and such as serve to distinguish it 
from all others. 
Propuctus costatus. Sowerby. 
I obtained imperfect specimens of a strongly costate Productus from the cherty limestone 
(Upper Carboniferous) on the banks of the Colorado, which approach more nearly to P. cos- 
tatus than any other described species. The shell is, however, narrower, the wings are less 
expanded, the cost broader, and the sulci separating them narrower than in any of the forms 
of P. costatus given in the figures of European paleontologists. 
From the Coal measures of Nebraska I have other specimens which correspond with P. cos- 
tatus, as recognized by our best authorities in Carboniferous mollusca, (Messrs. Norwood and 
Pratten, Shumard and Swallow,) closely. resembling the form of that species figured in De 
Konninck’s Monograph of the genus Productus, pl. VIL, figs. 3, 3a, 3b, but the spines of the 
cardinal border are smaller, those of the anterior surface much larger, and the strie more ir- 
regular than De Konninck represents them. There can be no doubt, however, that they rep- 
resent the same shell figured by De Konninck, (Monograph, plates VII and XVIII,) as that 
came from the vicinity of St. Louis, Missouri. 
It is perhaps possible that the marked differences which the American shells exhibit from 
those figured by Sowerby (Min. Conch. t. 560,) have a specific value, but as yet no one has 
been so well qualified to make this comparison as De Konninck, and he regards them as mere 
varieties of a common species. 
Propuctus costaTorpEs. Swallow. Trans. Acad. Nat. Sci. St. Louis, No. 2, p. 23, pl. 
I, figs. 8-8c. 
From the cherty limestone on the banks of the Colorado (near Camp 73) I procured speci- 
mens of a Productus apparently identical with that described by Prof. Swallow under the above 
name. From the smaller forms of P. costatus and other allied species, it is distinguished by 
the conspicuous pits which mark the smaller valve. For its more ready identification I tran- 
scribe the excellent description of Prof. S. - | 
‘Shell small, transverse, subrectangular; cardinal longer than the width of the shell; beak 
small, recurved scarcely beyond the cardinal border; ears large, thin vaulted and reflexed; 
dorsal valve, (ventral of Davidson) somewhat regularly arched, slightly flattened on the vis- 
ceral region, and toward the anterior border marked with broad depressed irregular long it 
dinal cost; of these, four on each side of the mesial sinus are much larger, and extend from 
the visceral region to the anterior border; the whole surface ornamented with large tubular 
spines, arranged somewhat regularly in diagonal lines; mesial sinus deep and broad, ventral 
valve, (dorsal, Davidson) strongly arched, slightly flattened on the visceral region, and toward 
the anterior margin; marked with longitudinal depressions corresponding to the coste of the 
