154 Trails. Acad. Sci. of St. Louis. 



must have been about 25 mm. in length, with a maximum 

 diameter of 10 mm. 



Straparollus ? sp. undet. 



Several imperfect specimens of one or more species of low 

 coiled shells, having diameters of 5 or 6 mm., have been 

 observed. They are too imperfect to allow their generic 

 characters to be certainly determined, but they seem to 

 belong to Straparollus. 



CEPHALOPODA. 



Orthoceras sp. undet. 



A single imperfect individual of a gradually tapering spe- 

 cies of this genus, is preserved in the collection studied. Its 

 greatest diameter is 6 mm., and the length of the fragment 

 preserved is about 14 mm. 



II. THE FAUNA OF BED NO. 4. 



MOLLUSCOIDEA. 



BRACHIOPODA. 



Chonopectus fischeri (N. & P.), 



PI. XIII. f. 1 7. 



This species occurs in the fauna of bed No. 4, but never in 

 such abundance as in the Chonopectus sandstone. The speci- 

 mens are not casts as in the sandstone, and often preserve the 

 fine surface markings which cannot be seen in the sandstone 

 specimens. These markings consist of exceedingly fine, more 

 or less interrupted radiating striae, and still finer concentric 

 striae with some coarser wrinkles of growth. The double 

 set of curved diagonal lines seen in many of the casts are not 

 so conspicuous in these limestone specimens, but they seem 

 to be more pronounced on the brachial than on the pedicle 

 valves. 



Pdgnax striatocostata (M. & W.). 



PI. XIII. f. 14-16. 



Original description. " Shell attaining a medium size, 

 subtrigonal, or sometimes approaching subpentagonal, mod 



