ORTMANN ! TERTIARY INVERTEBRATES. 
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individuals, belonging undoubtedly to V. triplicata, possess 16 or even 17 
ribs, while sometimes in the elongate form only 17 or 18 are present. As 
to the height of the upper whorls, there is no less variability : some spec- 
imens correspond to the proportions given by v. Ihering for V. quema- 
densis , while others correspond to those of V. philippiana , but many 
intermediate individuals are found. 
Even the development of the longitudinal ribs is not quite uniform, 
some specimens showing traces of an angulation near the suture, giving 
a suggestion of the series of tubercles found usually in V. triplicata. 
Thus, I can separate only a more slender form from V. triplicata , but I 
doubt very much that it is really a good species. Dali (1890, a, p. 314) 
and v. Ihering (1897, p. 305, and 1899, p. 32) have already suggested 
that all these forms may belong as varieties to one and the same species 
(, V. triplicata ). 
The recent Volutilithes philippiana Dali (1890, a, p. 303, pi. 9, f. 4) from 
the coast of Chili (677 fath.) is quite different from this fossil species, as 
is seen at once by the fact that it already has 6 whorls at a size of only 
36 mm, while in the fossil form of the same size hardly more than 3 
whorls are present. And, further, this recent form is a Volutilithes , while 
our fossil — in analogy with V. triplicata — seems to belong to Scaphella . 
Accordingly, the specific name of philippiana cannot be used for this 
fossil, and since gracilis of Philippi is preoccupied, we must adopt the 
name gracilior proposed by v. Ihering in 1896. 
A cast of this species has been sent to us by v. Ihering under the name 
of V. triplicata. 
Record of specimens : Mouth of Santa Cruz River, 7 sp. ; San Julian, 
Oven Point, 1 sp.; San Julian, Darwin Station, 2 casts; Upper Rio 
Chalia, 1 cast; Arroyo Gio, 1 cast. 
Distribution : Santa Cruz (Phil., v. Ih.), Patagonian beds (v. Ih.) ; Jegua 
quemada, Suprapatagonian beds (v. Ih.). 
158. Voluta petersoni Ortmann. 
PI. XXXV, Fig. 6. 
1900 V. p. Ortmann, in: Amer. Journ. Sci., v. 10, p. 376. 
Shell elongate, fusiform. Whorls 5 (aside from the apex, which is 
broken off). Spire slender, conical, mouth apparently not much longer 
