THE NAUTILUS. 47 



of them have the keel as rounded as in 0. s. depressa (Ckll.) 

 and some have the color bands well developed. A striking fea- 

 ture of this district is the number of albinos occurring- in both 

 pygmcea and obscura. Another unusual feature is the occur- 

 rence of three forms of Oreohelix intermingled. It is seldom 

 tliat I have found even two together until the season of 1917, 

 and never before have I found three together, yet at all of the 

 stations in White Creek Canyon this occurs. These stations 

 are really different portions of one great colony, as scattered 

 dead shells were found all along the canyon as far as we 

 traversed it, but Ave divided it into stations because of dif- 

 ferences in cover and other conditions, and variance in the 

 proportionate numbers of the several forms. 



A NEW PHIOTROCHATELLA FROM THE ISLE OF PINES, CUBA. 



BY WM. F. CLAPP. 



Peiotrochatella torrei, n. sp. 



Shell depressed, trochiform, thin, fragile, above with numer- 

 ous oblique plications, crossed by raised spiral lines ; below 

 sinooth; whorls, nine, the first smooth, white, the spiral lines 

 beginning on the fourth. Suture of early whorls simple, of 

 later whorls denticulate, and of the last two or three whorls 

 covered with a white moderately denticulate flange. Last 

 whorl descending slightly, aperture very oblique. Color yellow, 

 with irregular white patches and white denticulate sutural 

 flange above, uniform yellow below. 



Greatest diam. 13 mm., 1. d. IH mm., alt. 8 mm. Tj'pe in 

 Museum of Comparative Zoology, Cambridge, Massachusetts. 

 No. 36888. 



This species was discovered by Mr. \V. S. Brooks near the 

 southern end on the eastern face of the Sierra de Casas, Isle of 

 Pines, Cuba, and later a large series was collected by Mr. 

 Brooks and Dr. Thomas Barbour. 



No genus of the great host of West Indian land mollusks is 

 so famed for its beauty and delicacy of structure as Priotrocha- 

 tella. Hitherto but two well-defined species have been known, 



