192 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
Fam. TURRITELLIDAR Gray. 
Gen. TURRITELLA Lmck. 
123. Turritella exigua Ortmann. 
PI. XXXI, Fig. 12“-*'. 
1899 T. e. Ortmann, in: Amer. Journ. Sci., v. 8, p. 430. 
Shell small, with 10 whorls, about 4 times as high as broad at the base. 
Suture deep, whorls convex, with 5 to 7 spiral ribs, which are rather 
crowded, and often alternately stronger and weaker. The stronger ribs 
sometimes appear to be slightly granulated. 
Height, 15 mm; diameter, about 4 mm. 
Remarks : In the small size of the shell this species differs from all other 
Patagonian Turritella \ and agrees with the two dwarf forms described by 
Philippi from the Navidad beds of Chili: T. trilirata and parvula . But 
the latter can easily be distinguished by their flat whorls and smaller 
number of ribs. 
Record of specimens: Punta Arenas, horizon II (lower Magellanian), 
over 100 sp. 
Affinities : As regards the sculpture and the convex whorls, this species 
finds many analogous forms in Eocene, Miocene and Pliocene beds, as 
the type of which we may take the Oligocene and Miocene T turns Bast, 
of Europe. But taking into consideration the small size of the present 
form, we find that the species younger than Eocene are very much larger, 
and only in Eocene beds do we find a few that might be compared with 
our species in this respect also. One of the most closely allied forms 
seems to be : T. granulosa Deshayes, from the Eocene of France, but this 
one is still considerably larger than T. exigua and the whorls increase 
more rapidly. 
124. Turritella ambulacrum Sowerby. 
PI. XXXI, Fig. 13 0 - 6 . 
1846 T. ambulacrum Sowerby, in: Darwin, Geol. Observ. S. Amer., p. 
257, pi. 3, f. 49. 
1846 T. suturalis Sowerby, ibid., p. 257, pi. 3, f. 50. 
