1 86 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY 



Distribution: This species has not been found previously in the fossil 

 state, but is known living from the Falkland Islands and the Straits of 

 Magellan along the western coast of South America. 



Fam. NATICID^ Forb. 



Gen. NATICA Lmck. 

 117. NATICA CHILOENSIS Philippi. 



PI. XXXIII, Fig. i tt <>>. 



1887 N. c. Philippi, Tert. & Quart. Verst. Chiles, p. 89, pi. 10, f. 12. 

 1899 A 7 ! c. Ortmann, in: Amer. Journ. Sci., v. 8, p. 431. 



Shell ovate, thick, smooth, except for lines of growth. Spire conical, 

 about y of the height of the shell. Umbilicus small. Callus very thick, 

 covering most of the umbilicus. Mouth ovate, not dilated. 



Measurements of a very large specimen : Height, 34 mm, diameter, 

 25 mm, height of mouth, 21 mm; of a smaller one: height, 24 mm, 

 diameter, 19, height of mouth, 15 mm. 



Remarks: This species is recognized by the oval outline (which is, 

 however, a little variable), by the thick and solid shell, and the thick cal- 

 lus. The callus leaves only a narrow slit open at the umbilicus. 



N. gance of Philippi (Cretaceous of Quinquina) is allied, but has a 

 higher spire .(one-third of the height of the shell), while in N. chiloensis 

 it is between one-fourth and one-fifth, rarely more than one-fourth. The 

 external form is a little variable in our species, some individuals being 

 more rounded. The callus of the inner lip is very thick, suddenly nar- 

 rowed near the umbilical region, leaving a narrow, oval or crescentic 

 opening at the umbilicus. The suture is not impressed : in larger indi- 

 viduals, however, where the outer layer of the shell is exfoliated, the 

 suture appears as a deep groove giving a scalariform appearance to the 

 spire, a feature which reminds one of N. chilina and auca d'Orb. from 

 Puerto de Hambre. 



One individual from horizon III (upper) has the callus in the umbilical 

 region broader, with the slit hardly visible, and approaches thus (as also 

 in the more globular form) N. pachystoma Hupe from the Navidad beds 

 (see Philippi, 1887, pi. 10, f. la), to which also N. barroisi Phil, seems to 



