140 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
Affinities: In sculpture, this species is closely related to the two fore- 
going. It is represented in the recent seas of Chili and Patagonia by V. 
antiqua Kg. (see: v. Ihering, 1897, P- 2 53 )- 
66. Venus darwini Philippi. 
PI. XXVIII, Fig. 4. 
1887 ^ d* Philippi, Tert. & Quart. Verst. Chiles, p. 122, pi. 17, f. 2. 
1899 V. d. v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 19. 
Shell ovato-orbicular, subquaclrate, convex. Posterior dorsal margin 
convex, forming an indistinct angle with the posterior margin. Anterior 
extremity distinctly narrower than posterior. Apex at about one-fifth of 
the length. Area indistinct, nymphae immersed. Lunula lanceolate, 
depressed in the middle. Surface with regular, rather widely distant, 
elevated concentric lines, and very slight indications of radiating striae. 
Inner margins crenulate. 
Length, 73 mm; height, 65 mm; diameter, 17 (x 2) mm. Apex at 15 
mm from anterior end. 
Remarks: Radiating striae are not shown in Philippi’s figure, and, 
indeed, there are hardly any traces of them in our specimens. 
This species corresponds in size to V. wlckmanni, but is more elon- 
gated, and the concentric lines are a little more widely distant in V, volck- 
manni . There is also a slight resemblance to V. difficilis (see above), but 
in the latter the posterior end of the shell is narrower, and the surface 
ornaments are quite different. 
Record of specimens : Mouth of Santa Cruz River, 2 right, 4 left valves 
(in matrix). 
Distribution: Patagonian formation of Santa Cruz (Phil., v. Ih.). 
Affinities: Closely allied in form and sculpture is V. burdigalensis 
Mayer (see: Lloernes, 1870, p. 129, pi. 15, f. 1) from the Miocene of 
Europe, but the latter differs in the more closely set, and more distinctly 
lamellar concentric lines, and further, in V. burdigalensis , the hinge 
makes a transition to the genus Meretrix , while V. darwini seems to be 
a true Venus. Philippi and v. Ihering do not describe the hinge ; in our 
specimens only part of it is seen, and seems to possess, in the left valve, 
only three teeth : at any rate, I do not see any trace of a fourth (lunular) 
tooth ; this part of the hinge, however, is incompletely exposed. 
