234 
PATAGONIAN EXPEDITIONS ! PALEONTOLOGY. 
suture, and covering the tubercles of the preceding whorls. Surface smooth, 
only with lines of growth. Last whorl large and inflated. Mouth wide. 
Columella with three plaits, the uppermost of which is very indistinct. 
Height, 74 mm (apex damaged); diameter, 56 mm. 
Remarks: This is distinguished from the other Patagonian species by 
the very short spire and the strong nodes on the last whorl. Our indi- 
viduals are considerably smaller than v. Ihering’s (height, 156 mm; diam- 
eter, 100 mm), hardly half as large, and the slight differences that may 
be noticed between our figure and that of v. Ihering are, no doubt, differ- 
ences of age. 
The cast from Lake Pueyrredon is very poor, but the general form 
agrees, and there are also indications of the nodes. It cannot be united 
with any other species, but compares well with this one. 
Record of specimens : Mt. of Observation, upper horizon, 2 sp. (one of 
them very small); Lake Pueyrredon, 6oo' above base, 1 cast. 
Distribution: La Cueva, Suprapatagonian beds (v. Ih.). 
Affinities: V. brasiliana Sol. (Reeve, 1851, pi. 5, f. 34; Tryon, 1882, 
p. 98, pi. 29, f. 1 13; = V. colocynthis Chemn., Lahille, 1895, P- I0 > pi- b 
f. 3, 4, pi. 5) seems to be the descendant of V. ameghinoi, as has been 
pointed out already by v. Ihering. 
V. pacifica Sol. (Zittel, 1864, p. 38, pi. 15, f. 4, and Hutton, 1873, p. 
7) also resembles this species, but is more slender. It has been found 
from the Oamaru (Oligocene) beds to Recent times in New Zealand, and 
apparently V. atkinsoni Pritchard (1896, p. 100, pi. 3, f. 1) comes very near 
to the latter. It is from the Table Cape beds of Tasmania. 
Note. — It is an extremely interesting fact that the three types of fossil 
Patagonian Volutes , V. dorbignyana, V domeykoana , and V. ameghinoi are 
still represented on the Patagonian coast by very closely allied forms, 
namely : V. ancilla, V. magellanica , and V. brasiliana. This brings the 
fauna of the Patagonian beds into close relationship with the present 
Patagonian fauna, and makes it probable that the interval of time is not 
very great. 
The type of V. triplicata is no longer represented in the Recent South 
American waters, at least not by very closely allied forms. But we have 
seen that V. triplicata is linked to this recent group through V. dorbig- 
nyana , so that we may say that all the known Tertiary and living Volutas 
from Patagonia belong to one and the same stock. 
