Bd. III: 7) 
ANTARCTIC FOSSIL BRACIIIOPODA. 
13 
Hemithyris antarctica, sp. n. 
Plate I, figs 8, 9. 
Description: Subtrigonal, tumid, dorsal valve the deeper; ventral valve with 
broad sinus; both valves marked with irregular concentric lines of growth, but with- 
out any radial markings; beak somewhat long, sharp, produced and curved; foramen 
large. Colour, presumably, brown horn-colour, 
Rcmnrks: There are two species with which this has to be compared — the 
common boreal species Rhynchondla psittacca, and the Japanese species Rh. Wood- 
luardi, Adams (Jap. Brach. 100) considered by Davidson (Recent Brach. 168) to be 
a variety of the first named. 
P'rom R/i. psittacea this species differs in the same way as Rh. Woodzvardi is 
said to do — in the absence of the radial striæ which are so noticeable in R. psit- 
tacea. Otherwise it has the shape of some of the trigonal forms of R. psittacea 
(cf. Davidson, Recent Brach., PI. XXIV, f. 2); and it has the large protruding beak 
like that species. In this character of the beak the Antarctic fossils differ from 
R. Woodzvardi., which has a comparatively small beak with small foramen. 
The Antarctic specimens have been compared with examples of R. Woodzvardi 
identified by Adams : one in the Zoological Department, British Museum, and two in the 
Davidson collection. Geological Department of the same institution — ■ these two are 
the specimens figured by Davidson (Recent Brach., PL XXIV, f. 13, 13 a — c; not 
f. 12). The differences between the Antarctic and those Japanese examples are, in 
the former, a more trigonal shape, greater acumination posteriorly, and the larger 
beak: it is drawn too large and too pointed by Davidson in figs 13 a, b. 
Comparison of examples of R. psittacea and R. Woodwardi seems to justify 
the separation made by AdamS; and the Antarctic specimens agree with neither; 
they possess the beak of R. psittacea and the smooth test of R. Woodzvardi. Pos- 
sibly they were quite different in colour: not black, but brownish horn colour, unless 
fossilization has much altered them. 
Hemithyris antarctica must be regarded as the austral equivalent of the boreal 
species Hemithyris \_Rhvnchonel/a~\ psittacea; but it is remarkable that, with the 
possible exception of R. lucida; M‘Cov (see H. anstra/is), no examples of the 
H. psittacea-iorms have been found in the South American- Australian Tertiaries, and 
that no living austral forms are known. Apparently it was not uncommon at a 
comparatively late date in Antarctic history. 
On the other hand forms of the H. nigricans-sHxcr;, are common as fossils in 
Australasia and are still living. 
Locality: Cockburn Island (12), off Graham Land, Antarctica. 
