2IO PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



tudinal ribs, cancellated. Besides, there are distinct and regular lines of 

 growth. Spiral ribs, on the upper whorls, to the number of 4-5, 12-13 

 on the last whorl. They are sharp, but flat, equidistant, narrower in the 

 intervening spaces between the longitudinal ribs, but on the points of 

 intersection with the latter, they are slightly broadened, giving the 

 appearance of low tubercles. Longitudinal ribs 12-13 on eacn whorl, 

 rounded (not sharp), but distinct, running from suture to suture, but dis- 

 appearing on the canal. The lines of growth are very distinct, fine and 

 sharp, and very numerous. Mouth elliptical, canal comparatively short. 

 Outer lip crenulated within. 



Height, 16 mm; diameter, 6.5 mm. 



Record of specimens: Mouth of Santa Cruz River, 5 sp. 



Affinities: This species seems to be very closely allied to the Euro- 

 pean Miocene Fusus glomus Gene (Hoernes, 1856, p. 279, pi. 31, f. 2), but 

 the latter is less slender, larger, and the longitudinal ribs are less devel- 

 oped. The character of the spiral sculpture is essentially the same. 



Another closely allied form is F. nexilis Ball. (1890, p. 128, pi. 8, f. 4) 

 from the Miocene Silex-beds of Florida, but it is less slender, and the outer 

 lip has no crenulations. Another similar form, Chrysodomus glyptus Verr., 

 is found living in the West Indies, but this one has a larger mouth and 

 longer canal (see Dall, 1889, pi. 61, f. 82). 



141. CHRYSODOMUS PILSBRYI (Ortmann). 



PI. XXXIV, Fig. 3. 

 1900 Fusus p. Ortmann, in: Amer. Journ. Sci., v. 10, p. 375. 



Shell thick, elongated, fusiform ; spire a little shorter than the last 

 whorl. Whorls 7-8, convex, slightly appressed in the upper part near 

 the suture, ornamented with 8-9 strong, rounded, longitudinal ribs, which 

 are slightly oblique and curved. On the upper whorls these ribs reach 

 from suture to suture, on the last whorl they disappear at a short distance 

 below the middle. All of the surface of the shell is covered by very fine, 

 numerous, but distinct and subequal spiral striae. Lines of growth fine 

 and indistinct. Mouth comparatively small, continued into a compara- 

 tively short canal. Inner lip expanded, smooth; outer lip thick and ap- 

 parently without crenulations. 



Height, 36.5 mm (not quite complete at upper end); diameter, 12 mm. 



