194 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



I do not think that T. argentina is a distinct variety, but it is only the 

 younger, and better preserved state of the larger, and partly worn T. 

 ambulacrum. All our individuals of the typical T. ambulacrum show in 

 the upper part of the shell the sutural furrow less deep. The external 

 sculpture is essentially the same in both, only in old shells it is much 

 worn, and shows the striae less plainly, or not at all. 



V. Ihering, in 1899, hinted at the identity of T. ambulacrum, argentina 

 and steinmanni. 



Record of specimens : Mouth of Santa Cruz River, about 250 speci- 

 mens, and many fragments ; Paso del Rio Santa Cruz, 3 sp. ; Las Sa- 

 linas, 10 sp., and 6 doubtful chalcedony casts; Mt. of Observation, lower 

 horizon, 1 1 sp. ; Upper Rio Chalia, about 20 sp. (mostly casts) ; 30 miles 

 north of Upper Rio Chalia, about 40 sp. (mostly casts); Arroyo Gio, 18 

 sp. ; Lake Pueyrredon, base of Tertiary, 2 fragments ; Lake Pueyrredon, 

 600' above base, about 22 sp., and numerous fragments. 



Note: Some of the casts from 30 miles north of upper Rio Chalia may 

 belong to T-fiatagonica, since this species is also represented at this locality. 



Distribtttion : San Julian (Sow.); Santa Cruz (Sow., Roch. & Mab., v. 

 Ih.); La Cueva andjegua quemada (v. Ih.); Patagonian and Suprapata- 

 gonianbeds (v. Ih.). Navidadbeds: Navidad (Sow., Phil., Moer.); Ypun 

 Isl., Chonos Arch. (Sow.) ; Matanzas, Lota, Chiloe (Phil.). New Zealand: 

 Pareora beds (Miocene, Hutt.) and Wanganui beds (Pliocene Hutt. ; 

 Chatham Isl. (Hutt). 



Affinities: This Turritella is a characteristic type of the Patagonian 

 and Chilian Tertiary, and continues, in Chili through the Pliocene T. 

 cingulatiformis Moer. into Recent times, where it is represented by T. 

 cingulata (see Moericke). In Tertiary deposits of the northern hemis- 

 phere this type of Turritella is quite rare, but it is represented neverthe- 

 less. There is one species in the Miocene beds of Europe, which has 

 some resemblance to it: T. bicarinata Eichw. (Hoernes, 1856, p. 426, 

 pi. 43, f. 812). Especially what Hoernes calls the first and second vari- 

 eties (fig. 10, u, 12) much resemble our form in the deep suture and the 

 two strong spiral ribs. In this species, however, these two ribs are situ- 

 ated closer together (the upper one being more remote from the suture), 

 and there is no trace of an intermediate third principal rib. On the other 

 hand, the young shell of T. bicarinata is quite different from the young 

 T. ambulacrum, having only one principal rib. . But then again, T. bicari- 

 nata agrees in the lack of granulations -on the ribs. 



