158 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Shell umbilicated ; elevated, globose ; solid, coarse and rough with oblique 

 incremental striae intersected with delicate spiral lines ; color white, variously 

 marked with a single narrow band, or broader longitudinal and spiral patches 



Fig 64. 



Fig. 66. 



Fig. 66. 



Helix Cooperi 



of reddish-brown, sometimes uniformly red; suture impressed; spire elevated ; 

 whorls 5, convex, the last rounded, very decidedly deflected at the aperture ; 

 umbilicus moderate, pervious, one fifth the greater diameter of the shell ; aper- 

 ture very oblique, circular ; peristome simple, thickened, with its extremities 

 very nearly approached, and joined by a heavy white callus, that of the colu- 

 mella reflected. Greater diameter 20, lesser 16 mill; height, 13 mill. 



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 extremities. (Fig. 66.) 



Mr. IngersoU remarks : " This well-known Hclix^ 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 River Valley 

 we crossed a belt a hundred yards or so wide, and apparently 

 miles in length, where the surface was thickly strewn with 

 bleached shells, as though an army of these mollusks 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 num- 

 erous, crowded, subobsolete ribs, or coarse striae, crenellating 

 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 lino-ual dentitition of each form is alike, but I figure that «£ each. 

 In P. strigosa (PI. IV. Fig. H) there are 50 — 1 — 50 teeth, with 15 perfect 

 laterals ; c is an extreme marginal. 



P. Cooperi has (PI. IV. Fig. G) 29—1—29 teeth, with 11 perfect laterals. 



Helix Cooperi. 



