Lissarca. \ PELECYPODA. 855 



Type in the British Museum. 



Hab. Auckland Islands, in 10 fathoms. 



Remarks. Closely allied to L. rubro-fusca. Smith, from Kerguelen 

 Island, but of a different form, being less oblong, having the umbones 

 less terminal, and the hinge-teeth somewhat different. A faint depres- 

 sion is observable extending from the umbo down the posterior end. 

 (E. A. Smith.) 



2. Lissarca exilis, n. sp. Plate 51, fig. II. 



Shell very small, transversely trapezoidal, somewhat ventricose, 

 the beaks anterior, dorsal margin slightly raised, almost smooth, light 

 brown, sometimes radially rayed with white, equivalve, and very 

 inequilateral. Beaks slightly raised, tumid and rounded, approxi- 

 mate but not contiguous, situate very near the anterior end, at about 

 the anterior tenth of the length. Anterior end short, abruptly descend- 

 ing, and slightly convex ; posterior end much longer, keeled above, 

 the dorsal margin convexly elevated ; anterior margin and posterior 

 part of ventral margin regularly arched, the anterior part of the latter 

 straight. Area very small, linear. Sculpture consisting of fine con- 

 centric growth-lines, crossed by more or less distinct fine radiate 

 strife. Colour light brown to yellowish, very often with a few broad 

 white radial rays. Interior of the same colour, not shining, occasion- 

 ally with a few posterior radiate striae. Margins denticulate, but 

 smooth at the byssal foramen and the upper part of the posterior 

 margin. Hinge-plate narrow, arcuate, smooth in the middle, with 3 

 to 4 short and vertical teeth anteriorly, and 3 to 4 oblique teeth on the 

 posterior side. Ligament small. Adductor- scars inconspicuous, the 

 posterior scar larger than the anterior. Pattial line simple. 



Length, 3-2 mm. ; height, 2-2 mm. ; diameter, 2 mm. 



Type in my collection. 



Hab. Snares, in 50 fathoms (Captain Bollons). 



Remarks. This species is in the outlines similar to A. rubro-fusca, 

 Smith, but it is much smaller, constant in its form, of different colour, 

 and radially striate. 



3. Lissarca pisum, n. sp. Plate 51, fig. 12. 



Shell small, globosely oval, equivalve, very inequilateral, the beaks 

 anterior, light rufous, with fine radiate riblets. Beaks at or near the 

 anterior end, distinct, rounded, approximate, but not touching. An- 

 terior end descending almost straight or with a slight curve from 

 the urnbo, narrowly convex towards the basal margin ; posterior end 

 broadly oval, the dorsal margin raised and broadly convex, the pos- 

 terior margin regularly rounded ; anterior part of the basal margin 

 straight. Area very small, linear. Sculpture consisting of fine radiate 

 costse, very often indistinct, crossed by fine growth-lines. Colour light 

 reddish-brown. Interior of the same colour, dull. Margins denti- 



