67. CONTRIBUTION TO 



way as to make uncertain the presence or absence of an umbilicus. Its pres- 

 ence would remove our shell from Naticopsis. 



Transverse lines of growth cross the volutions, but apparently no other 

 6urfa<'e ornamentation. 



This fine shell comes from the Keokuk Group of Pitcher's Point, Salt River, 

 Ky., and the type specimen is the property of Mr. G. K. Greene. 



PLAT Y STOMA NIAGARENSE, Hall. Rowley. 



Plate 23. Fig. 12. 



We give here the side view of a specimen from the Niagara Group of Wal- 

 dron, Ind., with the outer vf)lution free from the rest of the shell, and directed 

 downward. This shell exhibits the most extravagant form of the species, and 

 might well be given a varietal name were it not that extensive collections at the 

 type locality show all grades of form from the lax to the closely coiled. 



The specimen illustrated is from the Niagara Group, Waldron, Ind., and is 

 the property of Mr. G. K. Greene. 



SPIRIFERINA HORIZON TALIS, N. Sp. (Rowley.) 



Plate 23. Figs. 13-14-L5-36. 



Valves unequal in length, the pedicil being quite one-third longer than the 

 brachial. The greatest convexity in either valve is nearer the anterior than the 

 posterior part of the shell and the greatest thickness at the middle of the pedi- 

 cal valve. 



A slight depression traveres the mesial fold, making it appear to be a 

 double plication. Ten simple plications either side of the mesial fold. 



A very indistinct elevation down the middle of the sinus. Ten plica- 

 tions on either side of the sinus. 



The shell is crossed with crowded lamellose lines of growth. Cardinal ex- 

 tremetJes pointed but not acute. Cardinal area the greatest width of the shell 

 and forms a low, broad triangle, confined entirely to the pedical valve. 



Tile horizontal position of the cardinal area where the shell rests on the 

 middle of either valve, is the chief character of this little brachiopod. The 

 character is constant, being shown by all the specimens before us, three double 

 and two separate valves. 



To the flattening of the pedical valve immediately over the cardinal area 

 is due tliis character. 



Tlie specimens were collected from the Warsaw limestone at Lanesville, Ind., 

 and now in the collection of Mr. G. K. Greene. 



