144 
PATAGONIAN EXPEDITIONS ! PALAEONTOLOGY. 
Gen. DOSINIA Scop. 
71. Dosinia magellanica spec. nov. 
PI. XXVII, Fig. 13. 
1899 D. complanata Ortmann, in: Am. Journ. Sci., v. 8, p. 429 (non D. 
complanata Ph i 1 . ) . 
Shell orbicular, compressed. Posterior dorsal margin forming, with the 
posterior margin, a regular, circular curve. Lunula ovate, concave, but 
elevated in the middle. Surface with regular concentric impressed lines, 
which are not very crowded to % mm distant from each other), dis- 
tinct all over the shell ; intervals between these lines perfectly flat, but 
near the anterior and posterior margins a little elevated. 
Length, 28 mm; height, 26.5 mm; diameter, about 4 (X2) mm. 
Remarks: In my first publication I made a mistake: I believed some 
fragments of Lucina neglecta (see above, p. 130) imbedded in the same 
piece of rock to belong to this species. But now, after succeeding in 
working them out of the matrix more satisfactorily, I see that we really 
have to deal with two different forms, and that the characters of the sur- 
face markings and of the curve of the posterior and dorsal margins, on 
which I founded the identification with Philippi’s D. complanata , are taken 
from individuals of the new Lucina. 
D. magellanica differs from D. complanata in the shell’s being a little 
more convex, in the posterior dorsal margin’s forming no angle with the 
posterior margin, and in the surface ornaments, which consist of impressed 
lines, not of elevated striae. 
In the following species ( D. meridionalis ), the curve between posterior 
dorsal and posterior margins is not regularly circular, but there is a sug- 
gestion of a blunt angle; the lunula is not elevated in the middle, the 
concentric ornaments are more irregular, and the intervals between the 
impressed lines are more or less convex; the shell itself is much larger. 
Record of specimens : Punta Arenas, horizon II (lower Magellanian), 2 
right, 1 left valves. 
Affinities: The most closely allied form seems to be: D. semi Levis 
(Artemis s ., Philippi, 1887, p. 1 13, pi. 13, f. 22) from Navidad, especially 
as regards the concentric lines, which are said to be “remote” from each 
