924 PELECYPOUA. [Eulamdlibranchia. 



Genus 3. NEOLEPTON, Monterosato, 1875. 



Neolepton, Monterosato, Atti Acad. Palermo, 1875, 12. Type : Lepton 

 squamosum, Montagu. 



Shell inflated, concentrically striate, more or less inequilateral, 

 impunctate ; hinge composed in the right valve of an anterior large 

 triangular tooth, surmounted by a hooked fine lamella, and behind 

 the central oblique resilium 2 diverging lamellae ; left valve with an 

 anterior hook-shaped cardinal and an oblique posterior lamella. 



Bernard considers the hinge of Neolepton as being very distinct 

 from that of Kellia and Lepton, and forming one of the primitive 

 stades in the series of the Heterodonta. Dr. W. H. Ball, however, is 

 of opinion that Monterosato's genus has only sectional value under 

 the genus Lepton. (Trans. Wagn. Free Inst., iii, pt. 5, 1139.) 



KEY TO .SPECIES. 



a. Shell thin and fragile, white, translucent ; anterior end slightly 



longer . . . . . . . . . . . . antipodum. 



b. Shell fairly solid, length only 2 mm., yellowish ; anterior end 



slightly shorter . . . . . . . . . . cilrinutn. 



c. Shell rather solid, whitish with red umbones, nearly equilateral sanguineum. 



1. Neolepton antipodum, Filhol, i860. Plate 53, figs. 11, o, b. 



Kellia inttipoiluiH, Filhol, Comptes Rend. Acad. Sci., xci, 1880, 1095 ; Miss. 

 I.C., 1885, 543 ; Huttori, P.L.S., N.S.W., ix, 526. Neolepton antipodum, 

 Filhol : Bernard, Bull. Mus. Hist, Nat.. Paris, 1897, 314 ; Medley, 

 T.N.Z.I., xxxviii, 74, pi. 1, f. 5. 



Shell very small, ovate-subrotund, inequilateral, pellucid, with 

 regular concentric striae. Beaks prominent, contiguous, small, inclined 

 forwards. Anterior end slightly longer than the posterior end, acutely 

 convex, the dorsal margin nearly straight, descending ; posterior end 

 broadly rounded, the sloping dorsal margin straight and shorter ; 

 basal margin regularly arched. Sculpture consisting of regular, fine, 

 sharp concentric lines. Colour white. Interior white, polished. Mar- 

 gins thin and sharp. Hinge : Right valve with a triangular large 

 anterior cardinal and a tine long posteriorly hooked lamella above it, 

 the resilifer under the beak, and behind it 2 rather long diverging 

 lamellae ; left valve with an anterior elongated lamella, hooked near 

 the resilifer, and with an oval tooth anteriorly, behind the middle an 

 elongated arid triangularly raised lamella. The anterior adductor-scar 

 is very small, the posterior scar oval and continuous with the pallia! 

 line. 



Diameter Ant. -post., 2-6 mm. ; dorse-ventral, 2-3 mm. : thick- 

 ness, 1 mm. 



Type in the Mus. Hist. Nat., Paris. 



Hab.- Campbell Island, Venus Bay ; under stones, near low- 

 water mark ; type (Filhol) : Bounty Islands, in 50 fathoms ; Port 

 Pegasus, Stewart Island, in 18 fathoms ; near Cuvier Island, in 

 38 fathoms (Captain Bollons) ; oft' Great Barrier Island, in 110 

 fathoms. Also Victoria (Gatliff). 



