86 STUDIES IN GEOLOGY, No. 3 



distinct, and in the upper whorls scarcely discernible. The 

 remaining two precarinal cords are close together. Those 

 behind the carina are equally spaced, the interspaces being 

 mere convex-sided v-shaped depressions. Lines of growth 

 are not evident. The line of smallest whorl-diameter is near 

 the suture in the earlier whorls, but in later whorls it is 

 nearer the keel, the surface curving outward to the suture. 

 Height of fragment bearing eight whorls, 75 mm. ; diam- 

 eter below, 25 mm. ; above, 6 mm. 



This variety differs from robusta in its more closely-set 

 sculpture. In this respect it is closer to T. ocoyana Conrad 

 (loc. cit.) from the Lower Miocene of California, than is 

 robiista; however, it differs from ocoyana in having a sharper 

 keel. 



Zorritos formation. Zorritos. 



Turritella charana n. sp. 

 IV Fig. 7. 



Shell of moderate size, the apical angle larger than that of 

 local related species. Whorls concave, with a pronounced 

 sharp keel at the anterior fourth. Before the keel the sur- 

 face descends, at an angle of about 45 "to the long axis of 

 the spire, to the suture, which marks the line of least whorl- 

 diameter. Behind the keel the surface is gently concave, its 

 angle with the long axis decreasing until at the suture it is 

 almost parallel to it. Sculpture of irregularly spaced spiral 

 cords or ribs, of which there are three before the keel and 

 seven behind it. The anteriormost cord borders the suture. 

 The second cord behind the keel is the strongest, and the 

 others are subequal in strength, the third above the keel 

 being possibly the least developed. Height of fragment 

 bearing 3^ whorls, 29 mm.; diameter below, 17.5 mm.; 

 above, 7.75 mm. 



This species is perhaps closer to T. ocoyana Conrad 74 



"Idem., pi. 7, figs. 73, 733, b. 



