Report of the State Geologist. 239 



top, rapidly contracting to a furrow upon each side, and then extend- 

 ing as a septum to the bottom of the valve. It has the appearance as 

 if the split tube had joined and formed a septum. Shell structure 

 undetermined. 



The name is proposed out of regard for Prof. C. L. Herrick, now 

 at the University of Cincinnati, who gave the first illustration of the 

 peculiar interior appendage. 



Syringothyrib ? PLENA. Hall sp. 



5piri/erpZe?ms, Hall, 1858. Geol. Surv.-, Iowa, vol. i, part 2, p. 603, pi. 13, 

 fig. 4. 



I have seen thirteen specimens of this species and find them 

 remarkably constant. They possess the external characters of Syrin- 

 gothyris, having a well-defined unplicated sinus and fold, shell structure 

 distinctly punctate and with the characteristic textile markings found 

 upon species of this genus. The ventral area is broad and strongly 

 arched, differing in this respect from all species of Syringothyris, 

 except S. herricki, from which it differs internally. The interior of 

 the ventral valve has two strong dental lamellae, which extend nearly 

 to the front margin. The extension of these lamellae is characteristic 

 of this species, and they are not half as long in any other species of 

 Spirifer. The fissure is almost completely filled by the transverse 

 plate, but I could not see any indication of the canal or the pointed 

 termination of the plate. I place this species provisionally in the 

 genus Syringothyris. 



Distribution. — Burlington limestone, at Burlington, Iowa; Quincy, 

 Illinois, and Pike county, Missouri. 



