Bd. III: 7) 
ANTARCTIC FOSSIL BRACHIOPODA. 
19 
Magasella australis, sp. n. 
PI. I, figs 14 — 16; Plate III, figs 3 a, 3 b. 
Description: Shell small, ovate, greatest breadth about the middle, tapering 
posteriorly and anteriorly, rounded in front. Dorsal valve convex, most so about 
the middle, whence runs a slight longitudinal depression, terminating as a shallow 
sulcus anteriorly. Ventral valve about as deep as dorsal, furnished with a slight 
but distinct median fold. Lateral margin almost straight, anterior margin distinctly 
folded to an M-shape; there being a median curve convex ventrally, on each side 
of which is a slight curve convex dorsally. Beak short, strong, slightly curved, 
truncated by an incomplete foramen, margined anteriorly by the umbo and by two 
small deltidial plates; beak-ridges not sharply defined. Surface marked by more or 
less coarse concentric growth-halts. Test finely punctate. Colour presumably, from 
indications retained, dull blood-red, rather stronger round umbones. Loop slender, 
attached to a somewhat massive broad hinge-plate, joining anteriorly a somewhat 
broad, scimitar-shaped septum, which is ventrally projected : reflected portion of 
loop wanting. 
Remarks: This species is most like Magasella alentica, Dall, as figured and 
'described by Davidson (Recent Brach. 95, PI. XVII, 16, 17) from metatypes pre- 
sented by Dall. The above description follows that which Davidson gives for 
M. alentica^ altered only where differences between the two forms require. Thus 
the distinctions between the species can be seen by comparing the two descriptions; 
and they are, principally, that the Antarctic species is not anteriorly indented, but 
rounded, it has a distinct dorsal sinus and ventral fold, a waved anterior margin, 
and conspicuous growth halts. 
Of the twelve species of Magasella described by Davidson in his Mon. Recent 
Brach, five are inhabitants of Austral seas and the rest of the Boreal. The present 
Antarctic species is evidently the Austral equivalent of the Boreal M. alentica; and 
it is possible that it may yet be found as a living shell in the southern seas. It 
is only in the southern seas that the Magasellœ have given rise to the higher 
forms of Magcllaninæ : in the northern seas they seems to have survived without 
producing such forms; for the Dallininæ of the northern seas have not come through 
a magaselliform stage. 
If the present species be compared with the narrow form of Tcrebratella rubi- 
ennda (Davidson, Recent Brach. XV, 17) it will be seen that at a very much 
smaller size it shows similar, though less pronounced characters, especially the 
dorsal sulcus and the ventral fold. 
This species has some likeness to Tercbratella ? pentagonalis, Tate of the 
Aldinga glauconitic Limestone, (Lower Murravian) South Australia; but that species 
