OF DENISON UNIVERSITY. 
49 
abundant fossils in the shales and limestones of the coal measures. 
Fig 25 illustrates the structure of the interior of the valve. 
Productiis inuricatus, N. and P. 
Fhis form, often called a variety of the above, differs so constant- 
ly from P. longispinus as to be worthy of a distinct name. It is less 
common than the above and may be recognized by the fact that the 
striae are much coarser than in P. longispinus, and especially by the 
concentric wrinkles upon the dorsal part of the ventral valve, which 
inclines to become flattened in one plane. 
Productiis Jfebrascensis, Owen. 
(Plate II, Fig. 30.) 
This widely distributed species is recognized by the peculiar no- 
dulose character of the surface, the coarse radiating striae being 
crossed by irregular concentric ridges. 
Productus costatus is very similar, as is P. semireticulatus. 
Both last named species probably occur in these beds, but as the 
specimens do not now lie at command they are not enumerated. 
Chonetes inesoloha. 
Although not figured, this is one of the most abundant and char- 
acteristic fossils of the region and may be known by the prominent 
mesial fold. Its known vertical range in the county is over one 
hundred feet. A figure can be found in Dana’s Manual p. 332. 
Stricklanddnia i?) suhquadrata, sp. n. 
(Plate I, Pdgs. 14, 14a.) 
The generic reference is simply provisional, but the figures will 
illustrate the specific characters. One specimen is in the form of a 
cast showing some of the internal markings; these in some respects 
resemble Pentamerus. The general outline is almost exactly that of 
Lingula subquadrata of the Silurian, being subquadrate with parallel 
sides. The beaks are moderately prominent and the valves quite 
strongly convex. The shell is marked by rather strong distant striae 
