ORTMANN : TERTIARY INVERTEBRATES. 203 



I think this form is only a variety of .9. ameghinoi, since we possess 

 individuals, which are in some degree intermediate, and especially the 

 number of nodes sometimes increases in S. ameghinoi to 17 and 18. 

 The other differences, number of spiral ribs, smaller size and more costi- 

 form appearance of the nodes, smaller size and more globular form of the 

 shell, are only differences in degree of development ; but at any rate, this 

 form is a very distinct variety. 



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

 Oven Point, 24 sp. (most of them poor) ; San Julian, Darwin Station, 2 

 sp. (poor) ; Shell Gap, Rio Chico, upper horizon, i sp. 



133. STRUTHIOLARIA ORNATA Sowerby. 



PI. XXXIII, Fig. i2 a -. 



1846 S. o. Sowerby, in: Darwin, Geol. Observ. S. Amer., p. 260, pi. 



4, f. 62. 



1887 5. o. Philippi, Tert. & Quart. Verst. Chiles, pi. i, f. 5 (after Sowerby). 

 1889 S. o. Rochebrune & Mabille, in: Miss. Cap Horn., v. 6, p. 40. 

 1897 S. o. v. Ihering, in: Rev. Mus. Paul., v. 2, p. 291. 

 1897 S- - var - densestriata v. Ihering, ibid., p. 291, textfig. 15. 

 1899 S. o. v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 27. 



Shell ovate, apex acuminate. Whorls convex, with unequal revolving 

 ribs to the number of about 20 on the last whorl. Upper part of whorls 

 deeply canaliculate at the suture, not angulated, with a series of about 15 

 costiform, elongated nodes. In the region of these nodes are about 12- 

 13 fine, subequal spiral ribs, in the lower part, just below the nodes, are 

 2 very strong ribs, followed by about 5-6 finer ones ; the uppermost of 

 the latter is sometimes a little stronger than the rest, and sometimes a 

 fine rib is intercalated between the two large ones. 



Height, 25 mm; diameter, 16 mm. 



Remarks: The canaliculate suture, and the two strong ribs just below 

 the nodes serve to distinguish this species at once. But it is to be re- 

 marked, that in rare cases only one of the larger spiral ribs is developed, 

 and even none at all. The latter form has been called by v. Ihering var. 

 densestriata. 



Sowerby's figure is very poor ; it represents a cast, and does not bring 

 out the most characteristic features of the shell. 



