16G 



A MANUAL OF AMERICAN LAND SHELLS. 



ing figures give various forms of the latter. I repeat the description of 

 the typical Gooperi: 



Shell umbilicated, elevated, globose, solid, coarse and rongb, with 

 oblique incremental striae intersected with delicate spiral lines ; color 

 Fig. 152. white, variously marked with a single narrow band or 

 broader longitudinal and spiral patches of reddish-brown, 

 sometimes uniformly red; suture impressed; spire ele- 

 vated; whorls 5, convex, the last rounded, very de- 

 cidedly deflected at the aperture; umbilicus moderate, 

 pervious, one-fifth the greater diameter of the shell; 

 aperture very oblique, circular; peristome simple, thick- 

 ened, with its extremities very nearly approached and 

 joined by a heavy white callus, that of the columella re- 

 var coopen. flg(.(-gj_ Greater diameter 20, lesser IG"""; height, IS™-". 

 The species varies greatly in shape, as seen in the figures given of 

 various forms. It is sometimes strongly carinated, and the peristome 

 is sometimes continuous by the heavy, raised callus connecting its ex- 

 tremities. (Fig. 15-4.) 



Mr. Ingersoll remarks: "This well-known 

 Helix, the largest of any collected, was not 

 uncommon in Middle Park and North Park, 

 Colorado, where great numbers of dead 

 shells would be found in isolated spots; / 

 only a few live ones being found in wet 

 places in the vicinity. In the Blue Kiver 

 Yallev we crossed a belt a hundred vards 



yia. 153. 



P. Cooperi. 



Tar. Cuoperi. 



or so wide, and apparently miles in length, where the surface was 

 thickly strewn with bleached shells, as though an army of these mol- 

 lusks had been overtaken on the march by universal destruction." 



Jaw (strigosa) long, low, slightly arcuate; anterior surface smooth 

 excepting near the lower margin, where there are numerous, crowded, 

 subobsolete ribs or coarse strire, crenelating the cutting edge. There 

 is a very strong muscular attachment to the upper margin. The jaw 

 of extreme forms of Cooperi is the same. 



The lingual dentition of each form is alike, but I figure that of each. 



In P. strigosa (Terr. Moll., Y, Plate IV, Fig. II) there are 50-1-50 

 teeth, with 15 perfect laterals; c is an extreme marginal. 



P. Coopen has (Terr. Moll., Y, Plate lY, Fig. G) 29-1-29 teeth, with 

 11 perfect laterals, 



