234 PATAGONIAN EXPEDITIONS 1 PAL/EONTOLOGY. 



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, 600' above base, I 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. 113; = V. colocynthis Chemn., Lahille, 1895, P- IO > pi- ! 

 f. 3, 4, pi. 5) seems to be the descendant of K 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. i) 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 Volutce, V. dorbignyana, V. domeykoana, and V. ameghinoi are 

 still represented on the Patagonian coast by very closely allied forms, 

 namely: V. ancilla, V. rnagellanica, 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 K 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. 



