MOLLUSCA.—HEDLEY. 21 
PHILIPPIELLA HAMILTONI Sp. NOV. 
(Plate L., figs. 8, 9, 10, 11.) 
Shell rather large and solid, inflated, unilateral, in shape passing from trapezoidal 
when young to mussel-form in the adult. Umbo terminal, projecting, dorsal margin 
straight, posterior and ventral margins rounded, anterior side concave above, convex 
below. Colour buff. Epidermis dense, persistent, developing about a dozen radiating 
rows of long dense bristles which project beyond the margin; between the rows the 
surface is closely latticed with transverse lamelle. Under the epidermis the surface 
of the valve is concentrically irregularly striated. Prodissoconch a simple semi-circular 
unsculptured plate slightly bulged. Ligament visible externally along half the dorsal 
margin. Hinge with a single stout tuberculate tooth in the anterior extremity of the 
left valve, which is independent in youth, but in the adult coalesces with the margin 
of the valve. Beneath it is excavated in the hinge plate a broad shallow byssal chamber. 
All the inner margin of the valve is smooth. Height, 6; length, 4-5mm. 
Thirty specimens were found by Mr. Harold Hamilton, after whom it is named, 
some embedded in sand and spongy growth below low water, January 2nd, 1913, in 
Lusitania Bay ; others on an old anchor recovered February 12th, 1918, at the Nuggets, 
Macquarie Island. 
This species differs from P. meleagrina,* for which it has, I think, been mistaken, 
by being much larger, by its Mytilus shape, by the ligament being continued beneath 
the predissoconch to the anterior side, and by being more excavate around the byssus 
orifice. 
PHILIPPIELLA ORBICULATA sp. nov. 
(Plate L., figs. 12, 13.) 
Shell large, compressed, discoidal, anterior side well developed. Colour buff. 
Surface glossy, concentrically engraved. Heavily draped with epidermis toward the 
margin, whence lines of epidermis stalks radiate to the umbo. Inner margin of the 
valve finely crenulate. This, which is perhaps the largest of the Philobryina, has the 
following dimensions :—Height, 15; length, 15; depth of conjoined valves, 5mm. 
Four, including type, December 28th, 1913, from 288 fathoms, ooze, off the Kastern 
Barrier of Adelie Land, in South Lat. 66° 55’ and East Long. 145° 21’; three more, 
January 22nd, 1914, from 120 fathoms, stony ground, in South Lat. 66° 8’ and Hast 
Long. 94° 17’. 
* Bernard.—Journ. de Conch., xlv., 1897, p. 12, pl. i., fig. 3. 
