290 PALEONTOLOGY OF OHIO. 



Length of a medium sized, mature specimen, 1.50 inches ; breadth, 

 1.90 inches ; convexity, about 1 inch. 



This species has much the general external appearance of Spirifer 

 Mosquensis of Fischer, as illustrated by Mr. Davidson from British speci- 

 mens, though its marks of growth show that the young shell was propor- 

 tionally wider, and its lateral angles more acute, than any of Mr. David- 

 son's figures would indicate, while neither he, MM. DeVerneuil, DeKon- 

 inck, nor any of the other authors who have figured and described that 

 shell, so far as I have seen, either mention or illustrate the beautiful fine 

 cancellated sculpturing seen on the species under consideration. The 

 most marked and decided difference, however, at least from the original 

 typical Russian examples of S. Mosquensis, is the very much greater de- 

 velopment and anterior extension of the dental laminae of the latter 

 species. 



It also resembles, though less nearly, the common S. striatus of Sowerby, 

 ■but may be readily distinguished by its proportionally less transverse 

 and more gibbous form, as well as by its less acute lateral angles, than 

 we generally see in that species, while its rostral cavity has a difierent 

 form. The minute cancellated sculpturing of its surface is also more 

 ■ delicate than that of S. striatus, var. dathratus (as illustrated by Mr. 

 Davidson), which is the only European form referred to S. striatus on 

 which markings of that nature have yet been illustrated by any of the 

 authors I have had an opportunity to consult. 



Prof. Swallow has described several species that seem to be more or 

 less similar to this, from about the same horizon in Missouri, with which 

 forms it ought to be compared. I have no authentic examples of these 

 Missouri shells for comparison, however, but so far as can be determined 

 from the published descriptions, none of them seem to agree exactly with 

 this shell. 



Locality and position : Waverly group of the Lower Carboniferous at Sciotoville 

 .and many other loeahties in Ohio. 



Spirifer (Trigonotreta) biplicatus, Hall?? 



Plate 14, fig. 5. 



Spirifer biplicatus, Hall (1858) ; Iowa Geological Report, I., part Palseont., 519, 

 Compare Spirifer Osagensis, Swallow (1860) ; Trans. St. Louis Acad. Sci., I., 641. 



Shell rather under medium size, trigonal-subsemicircular, with breadth 

 itwice to twice and a half the length, moderately convex ; hinge line 

 much longer than the breadth of the valves at any other point, and 



