I9O PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



Record of specimens : Mouth of Santa Cruz River, 4 sp.; 30 miles north 

 of upper Rio Chalia, i good specimen, 3 doubtful casts. 



Distribution: Santa Cruz (doubtful casts, according to Sowerby) (Roch. 

 & Mab.); La Cueva and Jegua quemada, Suprapatagonian, but not Pata- 

 gonianbeds (v. Ih.); Navidad beds of Chili; Navidad (Sow., Phil., Moer.), 

 Lebu (Phil.). 



New Zealand (Zitt), Pareora beds (Miocene, Hutt); Chatham Isl. 

 (Hutt). 



Affinities: This species comes near those which have been called by 

 the collective name of Natica heros, and are found from Miocene to Re- 

 cent times on the Atlantic coast of North America, and which are divided 

 by Dall (1892, pp. 372, 373) into three species. One of them, N. internet 

 Say, resembles our Patagonian fossil in the thick callus, but the callus is 

 not suddenly truncated at the umbilicus, the umbilicus is narrower, and 

 has a spiral rib inside, and further, the suture is more distinct. (I have 

 compared 4 specimens from the Miocene of St. Mary's River, Maryland, 

 one of which seems to be a true N. heros, the others belonging to N. 

 internet}. In N. perspective!, the suture is more like that of our species, 

 but it has a sharp umbilical rib, while in the true N. heros this rib is want- 

 ing, but the callus is less developed, and the suture deeper. Thus it is 

 hard to say, to which of these forms N. darwini shows the closest affin- 

 ity, but at any rate, it is closely allied to this Neogene group of species. 



121. NATICA SUBTENUIS v. Ihering. 



PI. XXXIII, Fig. 5. 

 1897 N. s. v. Ihering, in: Rev. Mus. Paul., v. 2, p. 284, textfig. 13. 



Shell ovato-subglobose, comparatively thin, smooth. Spire short, 

 suture inconspicuous. Umbilicus small. Inner lip with thin callus. No 

 callus on the columellar lip. Mouth large. 



Height, 40 mm ; diameter, 35 mm, another individual : height, 29 mm, 

 diameter, -24 mm. 



Remarks: This species is closely allied to the foregoing, but the shell 

 is thinner, the callus is less developed, the umbilicus narrower, the suture 

 a little more depressed, and the external form a little higher. 



Record of specimens : Mouth of Santa Cruz River, 2 sp. 



Distribution: Jegua quemada, Suprapatagonian beds (v. Ih.). 



