BRACHIOPOD A—THOMSON. 
35 
6 mm* length being in the Plati difarm stage. In this specimen the dental plates are 
already developed and there is no anterior median ridge in the ventral valve such as 
occurs in young stages of species of the Magellaninae. In the dorsal valve the elevated 
septum does not reach as far back as the cardinalia, and the hinge plates descend 
steeply from the socket ridges to the floor of the valve much as in early stages of 
Terebratella rubicunda (Thomson, 1915, No. 2). The next smallest specimen of 11 mm. 
length has just passed the Terebrataliform stage and shows no trace of the septum. 
The dimensions of the specimen chosen as the holotype are length 24 mm., 
breadth 22 mm., thickness 11 mm. A tendency to a straight front is noticeable on 
specimens as small as 13 mm. in length, but the specimen of 6 mm. is regularly rounded, 
with a dorsal valve slightly broader than long. 
Macandrevia vanhoffeni Blochmann. 
(Plate XV, fig. 10; plate XVI, fig. 43; plate XVII, figs. 57, 58, 59.) 
1906. Macandrevia vanhoffeni Blochmann, Zook Anz., Bd. XXX, pp. 696-697. 
1911. Macandrevia vanhoffeni Bidder, .Deutsche Siidpolar Exped., 1901-1903. 
Zook, Bd. IV, Heft. IV, pp. 391-392, Taf. XLII, figs. 8 a-b, 9 a-d, Taf, 
XLIII, figs. 14, 15, 21. 
Habitat.— Station 11, off Shackleton Glacier (Davis Sea), 358 fathoms, 31st 
January, 1914. Sea-bottom, ooze. 
The single adult shell is of moderate size, white in colour, and is rather broadly 
ovate with rounded sides and a slightly truncate front which is gently rounded. It is not 
so broad as Macandrevia lata and differs fron that species in the narrower and rounded 
front. The hinge line is broad and curved without a marked angle at the dorsal umbo- 
The convexity is moderate, the ventral valve assuming a slightly larger share. The 
folding is similar to that described above for M. lata , except that the anterior flattening 
of the valves is not so pronounced. The beak characters and dental plates do not differ 
from those of M. lata , and the cardinalia are of the same pattern, but the hinge plates 
are more approximate at their base and there is a small swelling just in front of the dorsal 
umbo which seems to represent a feeble cardinal process. The loop extends to three- 
fifths the length of the dorsal valve. The descending branches describe gentle outward 
curves from the middle line, making a total width of about one-third the width of the 
valve. The ascending branches are missing. The shell substance is thin, and the 
interior has a nacreous appearance. The growth lines are fairly prominent, and there is 
in addition a fine but irregular radial ornament which in the interior takes the form of 
faintly impressed radial grooves, most noticeable at a short distance on each side of the 
flattened middle longitudinal part of the dorsal valve. A fine radial ornament has been 
described by Dali in M. craniella, from which the present species differs by its greater 
breadth and less truncate front,. No such radial ornament has been described for M. 
vanhoffeni, but it is possible that it has been overlooked. It seems safest meanwhile to 
