SWALLOW — NEW VARIETIES OF SPIRIFER. 409 



concentric lamellae or folds, whose edges are fringed with 

 small thick set spines ; the bases of these spines form short 

 costae on the transverse folds, most distinct on the lower 

 edge, usually becoming obsolete on the upper part. The 

 folds are also marked with numerous concentric strite. This 

 variety is also marked with small, distant, radiating costae, 

 which are distinct from those formed by the base3 of the 

 spines on the concentric folds, and are more obvious when 

 the shell is partially exfoliated. It often has an obsolete or 

 sparingly developed sinus. 



This variety is common in the upper and middle Coal 

 Measures of Missouri; it is seldom found in the lower beds. 



SriEIFER CAMERATUS, MortOll. 



Variety, Kansasensis. 



This fossil is much wider in proportion; lateral extremities 

 often very much prolonged and mucronate ; it has more and 

 much smaller radiating costa?, often as many as fifty on each 

 side of the mesial sinus. In other respects it resembles the 

 S. cameratus. 



This variety was collected by Maj. Hawn in the Upper 

 Coal Measures of Kansas. 



Variety, percrassus. 



This shell is smaller, thicker, more convex, cardinal line 

 shorter than width of shell, area smaller, costae less numerous 

 (about sixteen on each side of the mesial sinus). 



This fossil maybe a distinct species, though it much resem- 

 bles the S. cameratus. 



Length, 1.13; width, 1.31; thickness, .88. 



This shell is common in the Upper Coal Measures of Mis- 

 souri and Kausas. 



Spirifer Kentuckensis, Shumard. 

 Variety, propatulus. 



This shell is three times as wide as long, and has ten sharp 

 plications on each side of the sinus. In other respects it 

 agrees with the S. Kentuckensis of Dr. Shumard. 



Length, .28 ; width, .84 ; thickness, .25. 



It is a rare fossil in the Upper Coal Measures of Missouri. 



Spirifer Leidti, Nor. & Prat. 



Variety, Chesterensis. 



This fossil is larger, more gibbous, the mesial fold and sinus 

 are not so abruptly depressed and elevated, but are more 



