238 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. 



Fam. PLEUROTOMID^. Stol. 



Gen. PLEUROTOMA Lmck. 

 165. PLEUROTOMA SUB^EQUALIS Sowerby. 



PI. XXXVI, Fig. 6. 



1846 P. s. Sowerby, in: Darwin, Geol. Observ. S. Amer., p. 257, pi. 4, 



f. 52. 

 1887 P. s. Philippi, Tert. & Quart. Verst. Chiles, p. 38, pi. i, f. 9. 



1899 P. discors v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 35 (non P. 

 discors Sowerby). 



1900 P. subcequalis Ortmann, in: Amer. Journ. Sci., v. 10, p. 381. 

 Shell turrite, elongate, subfusiform. Whorls seven, convex, upper part 



(above carina) slightly concave. Upper whorls with a tuberculiferous 

 carina in the middle and a number of spiral threads. Number of tuber- 

 cles on the carina, in the last whorl, about 12. Last whorl large, about 

 as long as the spire, or a little longer, with 3 prominent ribs below the 

 carina, which are slightly and indistinctly nodulose and finer spiral 

 threads on the canal. Mouth large, canal of medium length. Sinus of 

 outer lip situated on the upper tuberculiferous carina. 



Height, 23 mm (not complete); diameter 10 mm. 



Remarks: Our individual is larger than Sowerby's and Philippi's fig- 

 ures, but agrees well with them and with the descriptions, although 

 Sowerby mentions 5 ribs on the last whorl, which is, according to 

 Philippi, probably a mistake. Our specimen has, below the upper tuber- 

 culiferous carina, two strong ribs, followed by a very weak one, but the 

 latter is still stronger than the fine threads of the canal. 



I have no doubt that v. Ihering has made a mistake in the identifica- 

 tion of his P. discors. What he describes, in 1897, as P. discors var. 

 unifascialis is the following species, and what he mentions, in 1899, 

 under the name of P. discors is apparently the present one. For he 

 states expressly that the latter possesses three stronger ribs below the 

 carina, a character that belongs to P. subceqtialis, while in the diagnosis 

 of P. discors (Sowerby, 1846, p. 258), nothing of this kind is mentioned 

 and no traces of it are seen in the figure (1. c., pi. 4, f. 54). And further, 

 Philippi expressly states that P. discors is a Fusus, having no sinus on the 

 outer lip, while v. Ihering's P. discors has a sinus. 



