Vol. IV] DICKERSON— SIPHON ALIA ZONE, OREGON -^^9 



NATICA HANNIBALI, new species. 

 Plate 12, figures So and Sb. 



Shell large, with low, partially immersed spire and very large 

 subquadrate body-whorl; whorls five or six in number, the 

 penultimate whorl partially covered by body-whorl ; upper por- 

 tion of body-whorl and the penultimate whorl forming a some- 

 what flattened surface above which the small spire rises ab- 

 ruptly; sides of spire-whorls only slightly convex and sloping 

 away from the immersed linear suture with a uniform angle; 

 the portion of the body-whorl near the suture rising above the 

 suture and forming a distinct ridge; the portion of the whorl 

 a short distance below this ridge concave, making a groove 

 similar to that of the genus Gyrodes; a marked swelling below 

 this groove making a shoulder about a third of the whorl length 

 below the suture; anterior two-thirds of body-whorl only 

 slightly convex; peculiar incremental lines mark the body- 

 whorl and further emphasize its peculiarities ; these lines bowed 

 forward in the vicinity of the groove and outward on the lower 

 portion of the whorl ; outer lip simple ; inner lip incrusted by a 

 thin callus which completely covers the umbilicus, which is con- 

 tinuous with the outer lip; mouth very narrow anteriorly but 

 very broad near the base. 



Dimensions: Length, 42mm; width of body-whorl, 35mm. 



This species also occurs in the Tejon of Rose Canyon, San 

 Diego County, California, and in the Tejon about ten miles 

 north of Coalinga, California. Its very characteristic shape 

 renders it easy of identification. 



Type:— No. 243, Cal. Acad. Sci. Locality 25, Roseburg 

 Quadrangle, Oregon, near the center of Sec. 19, T. 26 S., R. 3 

 W., on the east bank of Little River at its confluence with the 

 Umpqua, underneath the bridge at that point. Coll., F. M. 

 Anderson. 



Named for Mr. Harold Hannibal, whose collections have 

 added greatly to our knowledge of the Tertiary Paleontology 

 of Oregon and Washington. 



