1922] Fauna from the Eocene of Washington 35 



equal to three times the width of the ribs ; finer spiral lines occur on the beveled 

 area and in the interspaces ; on the first eight or ten whorls of the shell, the 

 lower two revolving ribs are enlarged making a bicarinate sculpture ; on the 

 succeeding two or three whorls the three lower revolving ribs may be enlarged 

 while the remaining whorls will have the six revolving ribs of equal prominence. 

 Illustrations have been given to show the rib development. (Plate XI, Figures 

 13, 14, 16). Figures 13 and 14 are specimens of apical whorls which show the 

 bicarinate condition. Figure 16 is a specimen with both the apical and lower 

 whorls present. The change from the bicarinate through the tricarinate condition 

 to the uniform size of all the ribs is illustrated. 



This species has the same number of revolving ribs as T. olequahensis n. sp. 

 but differs from that species in the sides of the whorls being more oblique, and 

 the shell smaller. The ribs are sharper with the interspaces more concave. The 

 change in the prominence of the revolving ribs from the apex to the lower whorls 

 may be seen in many Turritellas. Specimens have not been found as yet which 

 can be definitely stated to be the apical whorls of the other species described 

 from the Cowlitz locality so that a comparison can not be made. 



Dimensions. Approximate altitude of shell 45 mm. ; width of lower whorl 

 8 mm. ; apical angle 18. 



Occurrence. At locality 329 (University of Washington Palaeontological 

 Collection) at bend in Cowlitz River near Vader, Lewis County, Section 28, 

 Township 11 North, Range 2 West. 



VADERENSIS n. Sp. 



Plate X, Figure 19 



Description. Shell large; sides of the whorls straight; suture very ap- 

 pressed; first revolving rib above the suture very sharp and protruding, below 

 this rib the surface is beveled to concave and contains two fine revolving threads 

 with finer, microscopic striae ; in the area above the lower, pronounced or 

 primary rib, between the rib and the suture above, there are two revolving ribs 

 of secondary size ; these ribs are smaller than the first but are still prominent 

 and tend to become nodose; between the lower secondary and the primary rib 

 below, there are two spiral threads, between which are finer, spiral lines ; between 

 the secondary ribs, as well as between the upper secondary rib and the suture, 

 there is a finer spiral rib or thread ; the finer ribs are minutely nodose. 



Dimensions. Width of median whorl 10 mm. 



Occurrence. At locality 329 (University of Washington Palaeontological 



