ORTMANN : TERTIARY INVERTEBRATES. 
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1873 T. ambulacrum Hutton, Cat. Tert. Moll. Ech. New Zealand, p. 12. 
1887 T. sowerbyana ( = suturalis Sow.) Philippi, Tert. & Quart. Verst. 
Chiles, p. 76, pi. 9, f. 2 (after Sowerby). 
1887 T. ambulacrum Philippi, ibid., p. 76, pi. 9, f. ia (after Sowerby). 
1889 T. ambulacrum and suturalis Rochebrune & Mabille, Miss. Cape 
Horn, v. 6, p. 43. 
1896 T. affinis Moericke, in: N. Jahrb. Miner., etc., Beil Bd. 10, p. 555, 
pi. 11, f. 3 (nee T. affinis Hupe, Philippi, Gray, see: Dali, 1892, p. 
3 ° 8 ). 
1897 T. ambulacrum v. Ihering, in: Rev. Mus. Paul., v. 2, p. 286. 
1897 ^ argentina v. Ihering, ibid., p. 286. 
1897 ^ steinmanni v. Ihering, ibid., p. 289. 
1899 T. ambulacrum and argentina v. Ihering, in: N. Jahrb. Miner., etc., 
v. 2, p. 25. 
Shell elongated, forming an angle of about 16 to"2i°. Suture in a 
deep furrow, whorls flat or slightly concave, with 3 principal revolving 
ribs, the upper and lower one the strongest, the middle one a little 
weaker. The upper rib forms a distinct angulation. Between the princi- 
pal ribs, 3 to 5 finer striae, and below the lower principal rib, 1 to 3 fine 
striae. Principal ribs, especially the uppermost, sometimes indistinctly 
crenulated by the lines of growth, but in no case with granulations. 
Height, 56 mm; diameter, 15 mm. 
Remarks: This species is on the one hand very variable, and on the 
other it assumes a different aspect according to the state of preservation. 
In young specimens the suture is not so deep as in older ones, and if the 
spiral striae are well preserved, they represent v. Ihering’s T. argentina. 
Large individuals show a very deep suture, and, as a rule, the surface 
ornamentation is destroyed to a great degree, so that the finer striae are 
in most cases completely obliterated, and only the three principal ribs 
remain. In many cases, only the upper and lower principal ribs are pre- 
served, and such individuals correspond to Sowerby’s type of T. ambula- 
crum. Individuals, in which the difference between the stronger and finer 
ribs is less pronounced, form v. Ihering’s T. steinmanni. In some cases 
the lower principal rib is indistinct, and such individuals are Sowerby’s 
T. suturalis [sowerbyana of Philippi). T. affinis of Moericke is a typical 
young T. ambulacrum ( = argentina v. Ih.). One must bear in mind that 
Moericke’s figure is 4 times natural size. 
