46 Trans. Acad. Sci. of St. Louis. 



Some of the Northview specimens are broader across the 

 flattened ventral side of the whorl than those figured by Meek 

 and Worthen, The entire surface is longitudinally fluted by 

 angular ridges from 1 to 2 mm. apart, and the outer flattened 

 portion is in addition covered by numerous fine longitudinal 

 striae. In the description of T. digonum only one style of 

 longitudinal markings is mentioned; whether this corre- 

 sponds to the flutings of the Northview specimens or to the 

 fine longitudinal striae is difficult to determine from the de- 

 scription, but judging from the illustration of the species, it 

 is the coarser markins;. If the fine lonofitudinal lines are not 

 present upon the original T. digonum, then the Northview 

 specimens doubtless represent a distinct species. The shell 

 is also marked by transverse striae of growth, nearlj'^ as fine 

 but less regular than the fine longitudinal striae. These lines 

 of growth are more conspicuous in the central portion of the 

 flattened ventral side of the shell, and bend backward from 

 the margins to the center of the ventral side so that the aper- 

 ture of the shell must have been deeply and broadly sinuate. 

 At the points where the transverse striae cross the longitudi- 

 nal flutings of the shell there are slight prominences which 

 are more conspicuous upon the lateral portions of the shell. 



ARTHROPOD A. 



TRILOBITA. 



Proetus sp. 



Two fragments of trilobites occur among the Northview 

 fossils. One is the glabella of a small species of Proetus ^ 

 and the other is a nearly complete pygidium which may 

 belong to the same genus or to Phillipsia. 



PJLANTAE. ? 

 Spirophtton sp. 



PI. VI. f. 2. 



There are present everywhere upon the weathered surfaces 

 of the Vermicular sandstone, flattened impressions marked by 

 moderately fine crescentic ridges which become more or less 



