BRACHIOPODA—THOMSON, 33 
large mesothyrid foramen not separated from the dorsal umbo by the deltidial plates, 
which are small and discrete. There are rather prominent growth lines in the first half 
of the shell, and again at three-quarters, the remainder of the shell being smooth. The 
pore density is 80 per sq. mm. 
The septum is long and junctions behind with cardinalia of the Magellaniform 
pattern. The loop is in the Magelliform stage. 
The other specimens agree nearly enough in all essential characters but are on 
the whole broader. They show a pore density of 70 to 87. 
The smallest specimen of 6 mm. in length deserves special mention. It was at 
first thought to be a specimen of Macandrevia in the Platidiform loop stage, but it does 
not possess dental plates which were observed in an undoubted Macandrevia of the 
same length in the present collection (see below), and moreover it possesses Magellani- 
form hinge plates. It must be regarded as in an abnormal Magadiniform loop stage 
in which the primitive hood has not yet been converted into a ring while the attachment 
of the primary lamellae has become very oblique and nearly reached the position usually 
attained in the Magelliform stage. This specimen shows a tendency to a straight front 
and is perhaps a different species from the others, 
Subfamily DALLINIAE Beecher. 
Genus MACANDREVIA King, 1859. 
Genotype TEREBRATULA CRANIUM Miiller. 
MACANDREVIA LATA sp. Ov. 
(Plate XVI, fig. 44; plate XVII, figs. 46, 47, 48, 49, 50.) 
Habitat.—Station 10; off Shackleton Glacier (Davis Sea), 325 fathoms, 29th 
January, 1914. Sea-bottom, ooze; temperature, 1-65° C. 
Material : one fragment of a dead shell and eight specimens taken alive, of which 
only four are fully adult. 
The shell is broadly ovate, as broad as long, and in shape most resembles 
Macandrevia americana Dall (1895) and M. vanhoffent Blochmann (1906) but is even 
broader than these species, and differs from both in possessing a straight instead of a 
rounded front. The hinge line is rather short and obtusely angled. The ventral valve 
is moderately convex and the dorsal valve flatter, the species repeating in these respects 
the proportions of M. americana and differing from M. vanhoffeni. There is no marked 
fold or sinus on either valve, and the commissures are practically plane, but a tendency 
to anterior retardation of the Cincta type is perhaps evidenced by a slight anterior 
flattening along the middle line of each valve, giving rise to the straight front. This 
flattening is, however, rather more pronounced on the dorsal valye. A similar 
¥20218—E Vou, IV, Parr 3, 
