222 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



151. Fusus ARCHIMEDIS Ortmann. 



PI. XXXIII, Fig. 20--. 

 1900 F. a. Ortmann, in: Amer. Journ. Sci., v. 10, p. 374. 



Shell fusiform ; spire shorter than the last whorl, scalariform. Whorls 

 over 5 (upper part of spire missing), very prominently angulated, suture 

 very deep. Upper part of whorls, above angulation, flat, obliquely 

 descending from the suture, lower part of upper whorls (below angula- 

 tion) very slightly convex, obliquely receding toward the lower suture. 

 Angulation blunt, with a number (1013) f blunt, often indistinct tuber- 

 cles. Sometimes these tubercles resemble indistinct longitudinal ribs, 

 running for a short distance downward. Surface of shell with fine revolv- 

 ing ribs on the lower part of the whorls and on the angulation, but these 

 ribs disappear on the upper part of the whorls at a short distance from the 

 angulation. Whole surface with distinct lines of growth, which have a 

 squamulose appearance where they cross the revolving ribs. Last whorl 

 large. Mouth triangular, continued into a long and straight canal. The 

 revolving ribs of the last whorl become indistinct on the canal. 



Height, 50 mm (but defective at upper end), diameter, 25 mm ; diam- 

 eter of a fragment, 31 mm. 



Remarks: Characterized by the strongly angulated whorls and deeply 

 receding suture. The larger part of the upper flat portion of the whorls 

 is quite smooth, except for growth-lines. Only near the angulation 3 to 4 

 revolving ribs begin to appear, and these ribs continue downward over 

 the angulation toward the canal, where they become indistinct. 



Record of specimens : San Julian, Darwin Station, 3 sp. 



Affinities: Only one species of this characteristic, strongly angulated 

 form is known from the South American Tertiary : F. oxytropis Philippi 

 (1887, p. 50, pi. 3, f. 15) from Navidad and Tubul, but this one is much 

 smaller, and the angulation much sharper, cariniform. 



I know only one other species that may be compared with ours : F. 

 hector Whitfield (1892, p. 199, pi. 25, f. 3-6) from the Eocene Marls of 

 New Jersey. But the latter is distinguished at once by the spiral sculp- 

 ture : the upper part of the whorls, above the angulation, does not possess 

 any spiral lines, and those below the angulation are much more distant 

 from each other and fewer in number. But, on the whole, the type of 

 sculpture is very similar in both species. 



