80 LAMELLIBRANCHIATA. 



longer ; dorsal margin angled behind ; hinge slightly curved. Height, 

 35 ; length, '7. 



Dead shells only. 



Australia. Peru. 



PECTUNCULUS. 



Orbicular, nearly equilateral, smooth or radiately striated ; umbones 

 central, divided by a striated ligamental area ; hinge semicircular ; 

 adductors sub-equal ; pallial line simple ; margins crenated inside. 



Widely spread. 



109. P. latiCOStatUS, Quoy, I.e., iii., p. 466, et P. ovatus, Quoy, 

 I.e., iii., p. 467. Orbicular, convex, thick, equilateral, with broad 

 rounded radiating ribs, which become obsolete towards the margin in 

 old individuals ; finely concentrically striated ; six or eight teeth on 

 each side, with a broad smooth area between them ; reddish brown, 

 interior white or brownish ; old shells are more or less truncated be- 

 hind, and the young are often varied with white. Height, 3 ; length, 3. 



Common. Chatham Islands. 



Found fossil in Australia, but not recent. The concentric striae 

 soon wear off, and the shell often becomes quite smooth. 



110. P. Striatularis, LamarJc, vi., p. 493. Orbicular, convex, 

 thick, sub-equilateral, umbones curved slightly forwards ; finely radi- 

 ately striate, and still more finely concentrically striate ; teeth, seven 

 to twelve on each side, not divided by a smooth space. Yellowish 

 brown, more or less irregularly marked with reddish ; interior varied 

 with brown. Height, 1 ; length, 1. 



Common. Stewart's Island. Australia. 



FAMILY 



Hinge with a great number of comb-like teeth, interrupted in the 

 middle by the ligamental impression ; interior pearly. 



NUCULA. 



Trigonal, with the umbones turned to the short posterior side ; 

 epidermis olive, margins crenulated ; hinge with an internal prominent 

 cartilage pit, and a series of sharp teeth on each side. 



Widely spread. 



111. N. margaritacea, Lamar~k, vi., p. 506. Obliquely ovate, 

 trigonal, smooth, margin crenulated ; hinge angular, with about eight 

 posterior and twenty-two anterior teeth, extending above the cartilage 

 pit. Height, '37 ; length, "37. 



Cook Strait. Auckland. Stewart's Island. Europe. 



112. N. Strange!, Adams. Oblong, very oblique, smooth, 

 covered with a pale olive epidermis ; thin, inflated, margin smooth ; 

 hinge with six posterior and ten anterior teeth. Height, "35 ; 

 length, '5. 



Wellington Harbour. Australia. 



113. N. COnSObrina, Adams and Angas, Proc. Zool. Soc., 1863, 

 p. 427. Obliquely ovate, inflated, rather thick, concentrically striated, 



