ORTMANN I TERTIARY INVERTEBRATES. 193 



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. la (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: Dall, 1892, p. 

 308). 



1897 ^ ambulacrum v. Ihering, in: Rev. Mus. Paul., v. 2, p. 286. 

 1897 ^ argentina v. Ihering, ibid., p. 286. 



1897 T. steinmanni v. Ihering, ibid., p. 289. 



1899 T. ambiilacrum and argentina v. Ihering, in: N. Jahrb. Miner., etc., 

 v. 2, p. 25. 



Shell elongated, forming an angle of about 16 to 21. 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, i 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. ambulacnim ( = argentina v. Ih.). One must bear in mind that 

 Moericke's figure is 4 times natural size. 



