372 Ortmann — Invertebrate Fossils from Patagonia. 



growth of the posterior part. The radiating furrow is nar- 

 rower, and is more inclined posteriorly, so as to render the 

 posterior part of the shell smaller in comparison with the 

 anterior. Length, 9 mm ; height, 4 mm . 



This does not seem to be an immature stage of M. patagonica. 



Santa Cruz. 



Gastropoda. 



15. Liotia scotti sp. nov. Shell small, rounded, flat above, 

 with a large, open umbilicus below. Spire with four rounded 

 whorls, increasing rapidly, suture deep. Last whorl with six 

 revolving, equidistant keels, the keel nearest to the umbilicus 

 the smallest, and disappearing within the umbilicus ; the upper 

 whorls show only the two uppermost keels. The keels are 

 crossed by very fine striae, and a number (15) of strong radial 

 ribs ; at the points of intersection of these ribs and the keels, 

 there is a small conical tubercle. Last whorl a little deflected 

 toward the mouth, which is circular and thickened. Height, 

 4 mm ; diameter, 8 ram . 



This species resembles much the recent L. acrilla of Dall. 

 Santa Cruz. 



16. Calliostoma ooservationis sp. nov. Shell low, conical, 

 not umbilicated. Whorls flat, last whorl on the periphery 

 bluntly angular. Above this angulation there are five distinct 

 revolving ribs ; near the mouth, between the second and third 

 (counted from above), a sixth rib begins to appear. In the 

 upper whorls the second and fourth ribs disappear, so that only 

 three ribs remain, besides the peripheral angulation, which 

 shows as a fourth rib immediately above the suture. All these 

 ribs, when fully developed, are snbequal, flattened, smooth, 

 about as broad as the intervals between them. The base of 

 the shell has 9-10 revolving ribs of the same character. The 

 outermost of them is not separated from the peripheral angu- 

 lation by a broader interval. Height, lQ-5 mm ; diameter, 12 mm . 



Mt. of Observation. 



17. Calliostoma cossmanni sp. nov. Shell conical, higher 

 than broad, not umbilicated. Whorls flat, the last one angu- 

 lated, with a keel on the periphery, which is wholly exposed 

 on the upper whorls, being situated close to, but above the 

 suture. Upper whorls with five revolving keels, the lower- 

 most, formed by the ' peripheral keel just mentioned, is the 

 strongest. It is smooth, with hardly any trace of granula- 

 tions. The uppermost and the third keel are stronger than 

 the second and the fourth ; the first, second, and third are 

 distinctly granulated, the fourth with finer granulations. 

 Toward the apex of the shell, the second and fourth keels dis- 

 appear, so that only three keels are present, the two upper 



