9o STUDIES IN GEOLOGY, No. 3 



a human finger-print. The flat tops of the threads are 

 crossed at right angles by very fine growth-lines, and in 

 places growth-wrinkles give them a wavy outline ; under 

 the microscope some of the wrinkles appear as deep sinuses. 

 The suture is distinct, the periphery rounded. The aperture 

 is very broad, and the peristome inclines backward. The 

 central base, hidden by irremovable matrix, is not known. 

 Height, 14; maximum diameter, 23.5 mm. 



This beautifully sculptured shell is somewhat similar to 

 S. obliqua Gabb, 78 from the Tejon Eocene of California 

 According to Gabb's figure obliqua has a much higher spire, 

 but a figure published by Dickerson, 79 which does not agree 

 with Gabb's, is closer to carolanum, although not identical. 

 Gabb's figure is very likely the faulty one. The sculpture of 

 obliqua is proportionally coarser than that of carolanum, and 

 obliqua is much smaller. In general appearance S. carol- 

 anum is something like S. nolani Maury, 80 from the Middle 

 Miocene of Santo Domingo, but the sculpture is more pro- 

 nounced in carolanum,, and it is much lower. S. multilineatus 

 Gabb, 81 from Sapote, Costa Rica, is also somewhat similar, 

 but differs in having a less oblique aperture and in being 

 higher. S. excentricus Guppy 82 is perhaps closer than any 

 other. It differs in having the aperture at a lower angle 

 than in carolanum, and in the ribs, which are rounded in 

 excentricus, flat-topped in carolanum. Guppy's figure and 

 description give little hint of the finer characters of the 

 sculpture. , 



Lower Zorritos. Quebrada Zapotal. 



78 Geol. Surv. Cal., Pal., vol. i, p. 109, pi. 21, fig. 112, 1864; (as 

 Naticina obliqua). 

 T 'Proc. Cal. Ac. Sci., ser. 4, vol. 5, pi. 5, figs. 5a, sb, 1915. 



80 Bull. Amer. Pal., vol. 5, No. 29, p. 139, pi. 24, fig. i, 1917. 



81 Jour. Ac. Nat. Sci. Phila., vol. 8, p. 339, pi. 44, fig. 6, 1881. 

 "Quart. Jour. Geol. Soc. Lond., vol. 32, p. 519, pi. 29, fig. n, 



1876. 



