152 PORPHYROBAPHE. 



88 (1848) ORBIGNY, Voy. dans 1' Amer. Merid., Moll., p. 295. 

 Helix (Cochlostyla) phasianella FER., Tabl. System, p. 48, no. 336 

 (nude name). ORB., Mag. de Zool., 1835, p. 7. 



The well authenticated range of this species extends from extreme 

 N.-W. Peru, and the neighborhood of the bay of Guayaquil, to Es- 

 meraldas in N.-W. Ecuador, including the island of Plata. It thus 

 inhabits both the arid coast region and the moister tract of low moun- 

 tains and coast, chiefly of tertiary or later age, though also ascending 

 the Pilaton valley to 1000 meters above the sea. There is no evidence 

 of its occurrence in Chili, the old citations being either erroneous or 

 based upon former temporary political boundaries. With one excep- 

 tion, all of the localities are in the Pacific drainage, Macas being the 

 sole place east of the main chain of the Andes whence it has been 

 reported. 



Cuming found it clinging to trees on the island of Plata, and in 

 such profusion that they looked as if laden with fruit. This is con- 

 firmed by Dr. Wolf. Others have reported it from inside hollow logs, 

 gregarious and in copious numbers. In consequence, the shell is 

 abundant in collections, though a sufficient account of the anatomy is 

 still to be supplied. 



Sowerby's original account, and all of the published figures, per- 

 tain to the form with only moderately thickened lip and spirally 

 striated last whorl. The spirals are sometimes very close, regular, 

 and though minute, still strong, especially on the heavily mottled 

 shells. The color varies from creamy brownish, paler above, to brown 

 and copiously mottled ; and there is often a pale band a little way 

 below the suture. 



Nine specimens in the series before me differ in having the spiral 

 striation obsolete on the last whorl, and the lip and columellar margin 

 greatly thickened and built forward beyond the reflection (pi. 50, 

 figs. 26, 27). This form may be called var. bilabratus. It is lustre- 

 less, without conspicuous spots. 



Var. bilabratus attains a larger size than the typical form, one col- 

 lected by Dr. Wolf measuring 82 mill. long. The tendency to form 

 a second or third expanded lip, leaving the former peristomes pro- 

 jecting as varices, is more usual than in thinner shells. 



Hidalgo, Dohrn and Reibisch have discussed the variations of P. 

 iostoma, but only the latter author notices the oblong, thick-lipped 

 form. Dohrn has called attention to the relationship existing between 



