NO. 1545. NEW FOSSIL MOLL USKS FROM CALIFORNIA— ARNOLD. 533 



Locality. — Head of Topanga Canyon, 3 miles south of Calabasas, 

 Los Angeles County, California. (G. W. Edmond and Ralph Arnold.) 

 Horizon. — Lower Miocene. 



CHLOROSTOMA (OMPHALIUS) DALLI, new species. 

 Plate XL, figs. 4, 4a and 46. 



Description. — Shell conoidal; spire somewhat elevated; apex obtuse; 

 whorls four, slightly convex, angulated just above the suture; portion 

 of whorl above angle crossed by (in the type twelve) transverse ridges 

 or waves running obliquely backward from the angle and appressing 

 against the antecedent whorls. Revolving ridge on angle, and, also on 

 body whorl, on a second equally prominent angle, at the base of the 

 whorl. Whole surface of shell, including base, ornamented by line 

 revolving lines (in the t3^pe there are four of these between the two 

 angles on the body whorl). Five equivalent narrow revolving fur- 

 rows also ornament the top of the bod}- whorl. Suture distinct. 

 Umbilicus deep and more or less effuse. Aperture circular; columel- 

 lar lip slightly twisted around umbilicus. Outer lip unknown. 



Dimensions. — Altitude, 10 mm.; latitude, 12.5 mm. 



Notes. — This species differs from Chlorostoma aureotinctmn Forbes, 

 to which it is allied, by the lack of the prominent furrows in the base 

 and the presence of the revolving furrows in the top of the whorl. 

 C. dalli is a variable form, no two specimens being exactly similar. 

 It grades into the two varieties next described. Named in honor of 

 Dr. William Healy Dall, of the United States Geological Survey. 



Tyj^e.— Cat. ^o. 16498-1, U.S.N.M. 



Locality. — Head of Topanga Can3^on, 3 miles south of Calabasas, 

 Los Angeles County, California. (G. W. Edmond and Ralph Arnold.) 



Horizon. — Lower Miocene. 



CHLOROSTOMA (OMPHALIUS) DALLI var. INORNATUS, new variety. 



Plate XL, fig. 5. 



Description. — Similar to C. dalli except that the transverse waves 

 are obsolete and the revolving furrows on top of the whorls are more 

 numerous and less prominent. 



Dhnensions. — Altitude, 10 mm.; latitude, 15 mm. 



Notes. — The t3'pe of this variet}^ is flatter than the typical form, but 

 this is due to crushing. 



Type.—Q,2X. No. 164986, U.S.N.M. 



Locality. — Head of Topanga Canyon, 3 miles south of Calabasas, 

 Los Angeles County, California. (G. W. Edmond and Ralph Arnold.) 

 LLorizon. — Lower Miocene. 



