36 AUSTRALASIAN ANTARCTIC EXPEDITION. 
ascribe the present specimen to that species, as the general shape is the same, and it was 
obtained from a neighbouring locality. The pore density varies from 115-120 mm. near 
the middle of the ventral valve, a valve differmg but slightly from that observed for M. 
vanhoffent, viz., 120-132. 
The dimensions of the specimen are :—length 20 mm., breadth 17 mm., thickness 
9 mm. 
From the same locality there is an immature specimen of 11 mm. in length 
which also shows the radial grooves on one side of the interior of the dorsal valve. It 
is relatively broader than the adult, and is a little broader than the growth lines of the 
latter at the same length, but is doubtless to be referred to the same species. 
Similarly a fragment of a dorsal valve, 4 mm. in length, from the same locality 
also shows the internal radial grooves. The loop and one side of the hinge are broken 
off, but there are the remains of a septum placed posteriorly but not reaching to the umbo. 
Obviously this fragment belongs to a young stage of the same species in the Platidiform 
loop stage. 
Macandrevia vanhoffeni differs from M. americana in being slightly narrower and 
less convex, and also, if the present species is correctly identified, in possessing a fine 
radial ornament. 
Habitat.—Station 10 off Shackleton Glacier (Davis Sea), 325 fathoms, 29th 
January, 1914. Sea-bottom, ooze. Temperature, 1-65° C. 
From this locality there are four adolescent shells differing from the specimens 
of M. lata occurring at the same locality in a less amount of frontal truncation combined 
with a more marked radial ornament. Three of them agree nearly enough in shape 
with M. vanhoffeni, but the fourth (length 9 mm. breadth 17 mm.) is relatively nearly 
as broad as M. lata, although without the straight front of that species. It may be 
regarded as a broad example of the present species. 
Habitat.—Station 2; lat. 66-55 8. long. 145-21 KE. (off Adelie Land), 288-300 
fathoms, 28th December, 1913. Sea-bottom, ooze. ‘Temperature, 1:8° C. 
From this locality there is a small specimen (length 13-5 mm., breadth 13 mm.), 
of broadly ovate shape with a rounded front, which also displayes the internal radial 
grooves in the dorsal valve. Its pore density is 103 persq. mm. A still smaller specimen 
of 8 mm. in length is rather narrower and also displays the radial ornament. 
Both contain dental plates, the larger being in the Macandreviform loop stage 
without a septum, and the smaller in what must at present (though incorrectly) be 
termed the Terebrataliform stage with a septum which does not unite with the cardinalia. 
These specimens must be tentatively referred to as M. vanhoffeni in the absence 
of adult shells from this locality, and greatly extend the range of the species to the Kast. 
