1 7^ PATAGONIA EXPEDITIONS : PALAEONTOLOGY. 
1887 ^ rug. Philippi, Tert. & Quart. Verst. Chiles, p. 83, pi. 9, f. 15. 
1897 (!>• ru g- v. Ihering, in: Rev. Mus. Paul., v. 2, p. 277. 
Shell large, solid, conical, elongate, not perforated. Whorls convex, 
with longitudinal ribs and spiral striae. Suture deep. Longitudinal ribs 
subequal, high, variciform, moderately thick in the young shell, very thick 
and swollen in the old, the anterior side (directed toward the mouth) is 
rounded, the posterior excavated, with a sharp edge. The number of ribs 
varies from 8 to 16 in different individuals, and even in one and the same 
individual the number sometimes varies considerably (for instance from 
10 to 16 in a large one from San Julian) ; other individuals preserve the 
number throughout (so a large one from San Julian with 8 ribs on all 
whorls). In young individuals, where the longitudinal ribs are thinner, they 
often show, on the upper part, near the suture, a small point or angle. Ribs 
and intervals crossed by revolving striae, which are more or less distinct 
(when indistinct, probably worn off). Base of shell with a spiral carina 
interrupted by the longitudinal ribs. Mouth almost circular, lip reflected. 
Measurements : Almost complete individual: height, 52 mm, diameter, 
18.5 mm; almost complete individual: height, 77 mm, diameter, 25 
mm; end broken off: height, 78 mm, diameter, 31 mm. 
Remarks: The number of revolving striae is very variable. The only 
difference from the Patagonian shell observed in the New Zealand fossil 
is the small number (8) of revolving ribs, but I possess from San Julian 
an individual of medium size that shows exactly this number, and younger 
ones that possess still less (only 6). In larger individuals this number of 
revolving striae increases considerably in the Patagonian shell (up to about 
20). S. browni is said to possess 16 to 18 longitudinal ribs, a number 
which is not supported by the figure : the last whorl, in the figure, has on 
the side directed toward the spectator only 6 ribs, which would bring the 
total number hardly over 15. Hutton says, that he does not see why 5 . 
lyrata should be different from S. rugulosa , and that S. browni is only a 
variety of S. lyrata , while Zittel regards S. browni as hardly distinguish- 
able from S. rugulosa. 
In my opinion, all these alleged species are forms of one and the same 
species, which varies in the number of longitudinal ribs, their thickness, 
and the development of the spiral striae. Indeed, among our material, 
the young ones completely resemble the figures of A. rugulosa, as well as 
of S. browni , and some of the larger ones completely resemble S. lyrata , 
