1910.] NATURAL SCIENCES OF PHILADELPHIA. 81 



Seven fully adult shells of the original lot measure : 

 Alt. 10, diam. 15 mm. 



This exact form has been found only at the type locality on the 

 south side of Cave Creek below the place marked Camp on the map, 

 p. 107, where it was taken in 1904, deeply imbedded in rotten shale near 

 the water's edge. About 30 specimens. 



In its native state 0. clappi is covered with humus, perhaps attached 

 by mucus. But few specimens were found except in the type Station. 

 Its habit of burying deeply in the soil probably accounts for its rarity. 



Elsewhere in Cave Creek Canyon a slightly different form (see 

 below) was found in 1906 at Stations 9, 11, 12, near 13, 14 and in the 

 ravine west of Reed's Mountain. These stations are all near the 

 bottom of the canyon. It was not found higher up. Here it occurs 

 with Sonorella, Ashmunella chiricahuana, A. ferrissi and A. angiilata. 



2. Lower Cave Creek Form. — The shells taken in 1906 at Stations 

 9, 11. 12 and near 13, 14, Cave Creek, are slightly more angular at 

 the periphery than the types, and the growth-wrinkles bear short 

 cuticular lamellae where they pass over the peripheral angle in fresh 

 and unrubbed individuals not fully mature. Often, but not always, 

 there are three circular rows of inconspicuous granules at wide, equal 

 intervals on the base, a weak or vanishing development of the basal 

 sculpture of 0. c. emigrans. The two brown bands (one at the outer 

 third of the upper surface of the last whorl, the other below and near 

 to the peripheral angle) are usually more distinct than in the type 

 lot of clappi. A small series of fully adult shells from Station 12 

 measure : 



Alt. 9, diam. 15.5 mm. 



