118 INVERTEBRATE PALEONTOLOGY. [WHITE. 



postero- dorsal margin sloping from behind the beaks to the posterior ex- 

 tremity, and apparently capped by a slender, accessory plate; posterior 

 extremity abruptly rounded; basal margin nearly straight; front regularly 

 rounded, both laterally and vertically; anterior gape consisting of a narrow, 

 vertical slit that occupies the middle of a somewhat prominent projection at 

 the antero-basal portion of the shell, which projection has the shape of a 

 Norman shield, as seen by front view, when both valves are in their natural 

 position i umbonal groove distinct and moderately deep, causing a distinct 

 groove upon the stony internal casts of the shell, which is of about the' 

 same dimensions and character as that which is left by the radiating internal 

 rib ; besides these two grooves, there is another, somewhat broader furrow 

 radiating from behind the beak of each valve to near the posterior end. A 

 broad, cake-like accessory plate covers the beaks and the space between 

 them; and, apparently, two others, one upon each valve, occupy the space 

 between the umbonal plates and the top of the Norman shield-shaped pro- 

 jection before mentioned. 



Surface marked by fine, concentric, raised lines, besides the radiating 

 furrows before mentioned. The masses of rock from which our specimens 

 were broken out, contained what appear to have been calcareous, siphonal 

 tubes, but none of them were found to be unmistakably connected with the 

 shells. 



Length, thirteen millimeters ; greatest height, seven millimeters ; breadth 

 at the front, six millimeters. 



Position and locality. Sulphur Creek Group; Upper Kanab, Utah. 



Gasteropoda. 



Genus RHYTOPHORUS Meek. 



Rliytoplionis Mcckii (sp. nov.). Shell subfusiform; spire moderately pro- 

 duced, nearly one-third as long as the entire length of the shell ; volutions 

 about six, convex, the last one somewhat large, elongate, convex, and taper- 

 ing from the middle toward the anterior end ; suture impressed, and upon 

 the proximal side of it there is an almost equally impressed revolving line, 

 having the aspect of a second suture ; folds of the eolumella well developed. 



Surface marked by the ordinary lines of growth and also upon the 



