CRETACEOUS FOSSILS. 127 



backwards and to the right. The outer lip is prolonged into two 

 long, slender, channelled spines, continuations of the carinae on 

 the whorl, which diverge rapidly, and which are not in the same 

 plane, the lower one heing directed much in advance of the upper. 



Figures, natural size. 



Abundant at Tuscan Springs, Tehama County. Collected by Dr. Ycatch (Divi- 

 sion A.). 



APORRHAIS, Petiver, Dacosta. 



A. FALCIFORMIS, U. S. 

 PI. 20, Fig. 83. 



Shell elongated, slender; spire very high; whorls usually 

 eleven, sometimes twelve; suture distinct; surface ornamented 

 by about fourteen rounded, longitudinal ribs, slightly curved and 

 narrower than the interspaces ; these are crossed by from seven 

 to nine rather large revolving ribs on the upper whorls. Body 

 volution somewhat uniangular near the lip ; the ribs dwindle to 

 mere broad, oblique tubercles, and the revolving lines extend 

 down to the canal. Mouth biangular above, rapidly narrowing 

 to the canal, which, from casts, appears to form nearly a third of 

 the total length of the shell. Lip long, falcate, sometimes almost 

 as high as the spire, usually ending about two-thirds of an inch 

 below the apex ; inner margin diverging at a small angle from 

 the spire ; outer margin nearly perpendicular and very slightly 

 convex, ending in an angle; lower margin concave, with a small 

 tubercle at its inner end. The shape of this side of the lip is 

 variable ; sometimes the angle is replaced by a broadly rounded 

 process. The inner face of this lip is angularly concave ; back 

 carinate. Columella incrusted by a large callus, forming a tuber- 

 cular projection immediately on the oblique lower surface of the 

 body whorl. 



Figure, natural size. 



Localities: Tuscan Springs, Dr. Veatch; Chico Creek, Mr. Brewer; Pence's 



