DESCRIPTIONS OF NEW SPECIES. 123 



This is the largest species of Goniobasis known to occur at the locality 

 where it was found, and which has furnished three other distinct species. 



The specific name is given in honor of Mr. W. Cleburn, division en- 

 gineer of the Union Pacific Railroad. 



Position and locality. Point of Rocks Group; Bear River Valley, near 

 Mellis Station, Wyoming. 



Goniobasis clirysaloidea (sp. no v.). Shell of medium size, gradually taper- 

 ing from the last volution to the apex; volutions about seven or eight, those 

 of the spire slightly convex, the last one broadly rounded to the anterior 

 end; suture impressed, the apparent impression being increased by the pro- 

 jecting fold of the distal edge of each volution, which is appressed against 

 the proximal edge of the next preceding one. 



Surface marked by more or less distinct longitudinal, slightly bent folds, 

 which are crossed by several revolving lines that appear only upon the folds 

 and not between them, giving them a knotted or crenulated appearance; 

 anterior surface of the last \olution also marked by distinct raised revolving 

 lines. 



Length twenty-eight millimeters; diameter of the last volution, nine 



O */ o 



millimeters. 



This species differs from G. chrysalis Meek in its much larger size, 

 much greater apical angle, straighter sides, and in the details of its ornamen- 

 tation. 



Position and locality. Point of Rocks Group; Bear River Valley, near 

 Mellis Station, Wyoming. 



Genus VIVIPARUS Montfort, 



Viviparus Pangmtchensis (sp. nov.). Shell elongate-trochiform ; spire 

 considerably produced in the case of some of the examples, but less so in 

 others, convex-conical, diminishing more rapidly near the apex than at the 

 proximal half of the shell ; apex acute ; volutions about six, flattened upon 

 the outer side, especially the last two volutions; anterior side of the last 

 volution broadly rounded and forming a more or less distinct angle with the 

 outer side; the distal side of each volution concave to receive the convex 



